Well I waded into this debate on the bus ride to work today morning, time now to dig up some stats and see if my intuition is right.
A disclaimer up front that I have done no stats check before my earlier comments, just was going off what I saw and what I felt, and I haven't watched them bowl in every test over the last few years, but have seen them both equally.
My gut feeling is that Ajmal looks a more dangerous bowler, can bowl as well as Herath can if he needs to hold up an end and dry runs, yet has that ability to run through sides that I feel Herath lacks, and as such it swung my vote to him. I feel that Herath, much like Vettori as someone compared him to earlier, can be sat on. That view may be heavily biased by the last few tests. It also may be because he looks so innocuous when he bowls. Anyways lets dig into the stats and see.
First I need to address this:
In the last 5 years, Herath has 18 5-fers and Ajmal has 9. I will leave you to decide who you will pick for taking 5 wickets
I expect you Simon to be clever enough to realise that having more five-fers isn't an objective measure of a bowlers wicket-taking prowess, but a subjective one that compares him to his teammates. Shakib takes a lot of five-fers, possibly more than a guy like Ajmal (I haven't checked), but that's more to do with him being the only bowler in the BD lineup capable of taking wickets than to do with him being a better wicket-taking bowler.
I went and dug up thier Averages, Econ and SR for their 5 wicket hauls starting form 2009 (Ajmal's debut):
Ajmal:
Bowling records | Test matches | Cricinfo Statsguru | ESPN Cricinfo
Herath:
Bowling records | Test matches | Cricinfo Statsguru | ESPN Cricinfo
First thing to point out - Ajmal has 9 five wicket hauls in 63 innings bowled. Herath has 18 in 75 innings bowled. Herath indeed has a much better rate in that regard. Ajmal has 1 5WI against a non-Top 8 though, while Herath has 2 5WI. So all in all you would like to give Herath the edge in this.
Initially I felt that Herath probably bowls a larger share of the overs and thus gets more opportunity to strike that Ajmal does. Then I noticed that Ajmal bowls, on average, 170 balls per innings and 210 balls when he gets a five-fer. Herath has 173 balls per innings and 215 balls per five wicket haul (during that period). Almost identical. So Ajmal isn't lacking in opportunity.
Another theory is that from 2009-2010 Herath had a few games alongside Murali. He has picked up 4 of his five-fers with Murali by his side. Maybe the pressure built by Murali was helping him. What are his stats since Murali retired?
Without Murali, Herath has 14 fiver fers in 61 innings bowled (still superior) and bowls a similar number of balls (172 per innings and 207 per five-fer). So clearly he's been doing a pretty fine job with or without Murali.
I then though that maybe Ajmal gets his five-wicket hauls quicker and cheaper than Herath does. Herath's five-fers might mainly come through long marathon spells on flat tracks when the other bowles have broken down or proven ineffective. This has already been disputed by seeing they both bowl similar number of balls for their five-fers, but I checked the stats anyways.
And indeed, Ajmal has a better strike rate, and average in his 5 wicket hauls, albeit by small margins. He even has a fractionally better economy rate. What does that mean? Not much given how minuscule the differences are. Ajmal's quickest five-fer took 24.3 overs (his 7-fer against England in Dubai), while Herath has 4 performances quicker than that (Australia 3 times in that list; which lends credence to the idea that Herath likes it when batsmen attack him).
I was expecting there to be a more significant advantage to Ajmal in average and strike rate than 2.34 runs and 2.7 balls respectively, but there you go.
So Herath does take five-wicket hauls a lot more frequently than Ajmal, but he isn't getting them at a better strike rate or average. Neither is he carrying his attack more than Ajmal, as they both basically bowl the same number of balls per innings normally and for their five-fers. So how is he doing it then? I feel I need to dig into the Pak team and SL team bowling stats during this period to fully understand each bowler's role in their team, and thus understand this.
But now back to my earlier hypothesis - Herath's diminishing effectiveness vs. Ajmal's continued brilliance. Lets see the career series-by-series stats for each of them. I have taken Ajmal's whole career (since he pretty much debuted as lead spinner) and Herath without Murali around (so 22nd July 2010).
However it must be noted Herath did play some Tests without Murali in 2009 - such as Ajmal's debut test, in which he took 4/15 in the second innings to defend 168. Ajmal was the not out man. Very poetic. I might dig up stats for Herath without Murali overall and not just 2009/2010 onwards and see what they look like, but for the sake of this debate lets say Herath's career as lead spinner started when Murali officially hung up his boots.
I expect them both to have started with a bang, with Herath's effectiveness slowly fading while Ajmal stays strong. Lets see if I'm right:
Herath:
http://stats.espncricinfo.com/ci/en...pan;template=results;type=bowling;view=series
Ajmal:
http://stats.espncricinfo.com/ci/en...s=1;template=results;type=bowling;view=series
Herath averaged under 30 in 6 of his first 8 series. He performed poorly in England in his second series as lead spinner - forgiveable - and against Pakistan in Dubai (a series where Ajmal averaged 28.77).
However in his last 7 series, he has averaged under 30 only twice, and once was against BD.
His best performances also have all come in Sri Lanka; he has averaged under 30 only once in 6 series outside (although to be fair 33.91 in Australia isn't terrible).
A more telling stats is in his last five series, his strike rate has been 73.7 - 40(bangladesh) - 95.6 - 86 - 78
As for Ajmal? Well he has been fairly inconsistent, it's hard to read a pattern. In his first 5 series, he had decent ones in Sri Lanka and England, but was bullied in New Zealand and Australia, and in UAE by South Africa. He then proceeded to demolish West Indies before being meh in Zimbabwe. He then strung together 4 series with an average under 30 but that included Bangladesh, before he went to South Africa and averaged 33 and tore apart Zimbabwe in two tests. Ripped South Africa apart back in the UAE, and just when you felt he was putting together a really impressive run, Sri Lanka visited UAE and he averaged 42 with a SR of 117 (Herath averaged 36.6 and a SR of 73 in comparison).
So my gut feeling that Herath started really well but faded seems to be true, while Ajmal didn't start with a bang but did string together about 9 series of pretty solid efforts in a row once he found his feet. However Ajmal hasn't wrecked a side in a series as often as Herath has.
Little bit more analysis shows the sides Herath has 'wrecked' (lets take that to mean an SR of 50 or less) have been West Indies, Australia, England, New Zealand, and Bangladesh. 4 of those sides aren't known to grind out runs and England are just terrible with spin. Also it must be noted that all 5 of these series have been in Sri Lanka. Herath also has a SR of 56 against Bangladesh in the other series he played against them, which was also in Sri Lanka.
Ajmal on the other hand has wrecked...West Indies, England and Zimbabwe, with an SR of 59 against the Saffars. His second and third series were New Zealand and Australia and he has yet to play them again. He has bowled to South Africa and Sri Lanka a lot and those sides are tough for a spinner to bowl to, which may explain why his stats don't match up to (my) expectations.
So what does this tell us? Nothing really. An hour of my life wasted on statsguru to prove that Herath may be in a decline and that Ajmal isn't as effective a wicket taking force as I felt he was, and that Herath was beastly on home pitches. Sigh.