I might have undershot a little with Wallace (although I think Wallace is actually a BETTER defender, but Smith is a much better rebounder), but KG, really? Do you mean 36 year old KG? Or 26 year old KG?
Because 26 year old KG was probably one of the top 10 players of all time, and a monster on both ends of the court.
Not to mention KG is 7'1", and a center. So, yes, if he was guaranteed to have the same year as last year, I think he would be worth the max...but that is as a 7'1" center. If he were a 6'9" power forward, I think he would be worth about $10-11 million per year.
Nonononono, I definitely mean 36-yo KG!! I'm not trying to talk anyone into Josh Smith being a hall of famer. =)
Regarding height and position, well, both players actually spent time last year at both positions. Smith may not be 7', but he still blocks shots at an elite, Dwight-Howard-like rate.
Regarding defense... like I said the stats are sketchy. For what it's worth, though, Josh Smith ranked in at 5th in defensive rating and 1st in defensive win shares last year. Those rating systems at least pass the smell test- I'm scanning the rankings and both top 20s include the names you would expect (such as KG, Tyson Chandler, Rondo, Lebron James, Joakim Noah, Serge Ibaka, Elton Brand, Andre Iguodala, etc). Smith ranks #4 in the league by hoopdata's defense metric (steals+blocks+charges taken).
Gerald Wallace is a very good defender, but he hasn't appeared in the top 20 of any of these since 09-10 season. The adjusted 2-year +/- numbers at basketballvalue.com like both players a lot, but they also put Smith up in the top 5 while Wallace ranks 18th.
Looking at the numbers, though, I'll admit I hadn't realized what a valuable player Gerald Wallace probably is defensively.