Sometimes this can result in good First-Class players failing to become good Test players, but under ANY circumstances a proven First-Class player is more likely to be successful in a Test starting tomorrow than an unproven or proven-crap one.
This is the only thing that I can't understand in your line of argument against Phil Hughes!
Hughes was at least the second best batsman in the shield this season before his selection (Klinger would be the one ahead of him) - and brief outings in the previous season showed the same sort of form that he had this season.
For the better part of 2 seasons, he was a FC batsman averaging 60 --> and at only 20 years of age!! Generally the young guys come in and make some good scores, but also chalk up some ugly innings - to average over 45 as a young player is a remarkable achievement (Michael Clarke picked for Australia on the back of FC centuries, but his overall record was under 45 when selected).
Hughes' record isn't just remarkable, it's astonishing that, at 20, he should be bettering the likes of Chris Rogers in the shield --> with the retirement of Hayden it opened up a spot and it was an
absolute no brainer to pick Hughes.
Especially when one considers that he scored so many runs that he forced the selectors to come and have a look, and then when they turned up scored a century and 80*.
Siddle's 24 FC average with the ball is also pretty special for a younger player - and, with the advantage of hindsight, I reckon I preferred Bollinger simply because he's a NSWman! The 2 bowlers had been pretty even over the last 2 seasons, but Siddle had the youth on his side, and was only going to get better against top line competition.
So - on the back of that essay, my selection tip would be:
if 2 players are fairly evenly matched, strongly consider the younger
(i) because they'll further improve their game against top level competition
(ii) because it's an investment - they'll be around at the top level for longer
Normally when a player has 20-30 tests under his belt he starts to feel like he 'belongs' at the top level and isn't so much playing for his spot, but rather out to dominate the opposition.
Giving a 32yr old 2 years might mean that you're now ready to choose a new player.
Giving a 22 year old 2 years then gives you a feasible 8-10 more years of their best play at the top level.
Having said all that - I think McGain was a good selection