Be unusual if these were both true wouldn't it? Anyway 5 years of 70+ is more impressive than 4 years of 70+ regardless
I guess it depends how you interpret the meaning of the first statement, but to me it makes sense, it just requires one lean year. For Ponting it's:
2002: 1064 @ 70.93, 5 centuries
2003: 1503 @ 100.20, 6 centuries
2004: 697 @ 41.00, 0 centuries
2005: 1544 @ 67.13, 6 centuries
2006: 1333 @ 88.87, 7 centuries
So he just had a weaker 2004, which included two subcontinent tours and an injury. Still averaged over 70 across the period, started the run with a test average of 43.78 and finished it at 59.38.
Overall I think there's an argument that Smith's run is more impressive because it really has no low points or weaknesses, but it's also over a shorter period so there's plenty of room for debate there. He could have a terrible year next up and Ponting's run would clearly look superior.
edit: Another small consideration is that Smith is younger. Ponting had just turned 27 at the start of that run with six years of test cricket behind him and finished it at 32, at which point he clearly started to decline a bit as a batsman, though he did make another 4000 or so test runs. Smith was 24 at the start of 2014, and they made their test debut at about the same age.