True enough as far as that goes, but a Dallas Thomas with great foot movement and hand strength at 265 is just not going to have the mass/strength/leverage required to drive a large defender back or hold his ground in pass protection as he will at 295.
All other things being equal for a DT, I'd rather have him weight 285 than 265.
There was an interesting analysis on Rocky Top Talk showing the highly correlated relationship of the weight of the defensive front seven and defensive ranking. Alabama had the heaviest front seven and the best defense. There were only a couple exceptions of a front seven being out of the top 20 in weight and ranking in the top 20 statistically.
Scheme has a lot to do with it. If you run a 2-Gap DL, then you need the big, space-eating DT's to clog their gaps. If you run a 1-Gap, then you need lighter, quicker DT's to get penetration. If Wilcox runs a 1-Gap, smaller DT's will be fine. He'll still need a guy to play NT over the 2nd gap (inbetween the Center and Guard), but at 270, Rae Sykes is big enough to play UT over the 3rd gap (straight across from the Guard). If he runs a 2-Gap, then missing those massive DT's will hurt. From everything I've heard and read, a 1-Gapper is right up Wilcox's alley. Small, quick DL and a LB corps that flows to the ball.
About Bama, the weight thing is just a coincidence. First off, they had Mt. Cody who was the biggest DT in the NCAA last year. Secondly, Saban runs a 3-4 DEF that I believe utilizes a 2-Gap DL. So you know how I talked about the Vols using a 2-Gap would need the two big DT's for our 4-3? Well for a 3-4 2-Gap, you not only need the massive NT but big 5-Tech DE's on the edge. These DE's were Brandon Deaderick (around 300 lbs.) and Lorenzo Washington (around 290 lbs.). Marcel Dareus, who started 4 games in Washington's spot, weighed 280 lbs. - we'll be seeing a lot of this guy; guy's a beast.
If the Vols put those 3 guys on our 4-3 1-Gap DEF, we wouldn't have the same success. Cody would struggle to get pass-rush that we'd want from him, Deaderick isn't an elite pass-rushing DT, and Washington would be the guy who'd have to play DE, which he wouldn't be able to get around the edge at. Yeah, helluva' run-stuffing crew, but when your pass-rush comes from your DL, you're not getting after the QB. It'd be good if they could all rotate, but not it they'll all starting - not even in a 2-Gapper.
Ok, so their 3-man DL alone weighs around 940 lbs, which is smaller than an ideal 4-3 1-Gap (I'd put that at 1,110 lbs. - RE: 260 lbs. LE: 270 lbs. UT: 280 lbs. NT: 300 lbs.), but that's big for a 3-4 DL and the ideal 4-3 DL has the extra man (and not many college teams have that ideal size for their 4-3) Then factor in the 3-4 LB's, which are bigger than 4-3 LB's. The OLB's need to have pass-rush ability, so they'll need bulk to take on OT's. The ILB's are about the same size as 4-3 MIKE's, but there are two of them in a 3-4. Rolando McClain was around 250 lbs. Cory Reamer is listed at 234. Eryk Anders at 227 lbs. Then two other guys handled the 4th spot: Dont'a Hightower, who is 260 lbs., and Courtney Upshaw, who is 263 lbs - we'll just split the difference ang go with 261 lbs., weighing on he lower side. So the LB corps weighs in at 972 lbs., which is light compared to the ideal. We'd actually be able to use their LB's in our 4-3, but only because Reamer and Anders are lighter than the typical 3-4 LB's. I'd put an ideal 4-3 LB corps to weigh a combined 730 lbs. (WLB: 235 lbs. SLB: 245. MLB: 250 lbs.), but that's a Cover 2, which would typically go with a 1-Gapper.
Don't get me wrong - size is a good thing. As long as it suits the DEF that's utilizing it. I think that's typically the case, hence the 20 or so other teams that fall into that line of thinking. But Wilcox can compensate and turn a weakness into a strength if he installs the right scheme.