As noted by others, great comaprison Dave.
A couple of questions (anyone):
1) If you use the BTS System, isn't it possible to take any of the boots and make them somewhat flex as you desire?
For example, I generally want an all mountain boot, more flex, and the Track 225 would probably be the best boot for that purpose, but I also want what I consider to be a stronger boot/ shell, the Track 325, not to mention I like the black/ red colors better. Could I put a BTS system on it and make it flex similar to the Track 225?
2)Using a comparison of one boot vs. another based on shell material and design: The Head Stratos Pro is noted as being stiffer than the Suzuka, but not as much as the Indy. I would guess that the plastic specs. (shore & elasticity) on the Head must be such that they are similar to the Indy, but because it has, what I would consider, a symmetric design like the Track (SB) series it is not as stiff as the Indy. If this is true, and I don't know if it is, wouldn't that make the Track 325 stiffer than the Suzuka?
Also, Dave, another nice comparison might be a recommended rider weight range for each of the boots as it relates to the ability to flex the boots. Bomber has general information of this nature on their store site for the current models, but not for the new Tracks.