Unless you have a 6 dex, you should just go for fullplate, and if you have 6 dex you REALLY need the extra point anyway. At worst, you can bum a Cat's Grace off a friendly caster or a wand, and that will give you your bonus, even at 8 dex.

I think the only time it really matters is when making dragonhide plate, but not too sure.

Yeah, you only need a dragon 3 sizes larger for half plate, whereas you need 4 sizes larger for fullplate or breastplate.