Hey BB- Here's my take on it.....No, the VX doesn't take any special battery...us neurotic owners just tend to fuss over things like this a bit more than normal folks..
I think the Optima has been so popular because of a couple reasons I can think of...it claims to be 15x more vibration resistant, it can be placed in any orientation, it's sealed and won't leak, and maintenance free. Since many VX owners have added high electrical load items such as stereos, amps and lights, etc.., the Yellow top & Blue top "claim" they handle that load "better" than most other batteries. The vibration resistance factor is a key reason Dave & I are interested in them since we drive about 2 miles on dirt/rocky roads every day .
But I guess there's also a bit of illogical reasoning too...it looks good!
And thanks for a ton of good info Eric!