IMHO from my short hit radical pro is actually more stable on off center hits (i guess due to cap) but its pretty close at similar weight specs.
When I compared Tgk 260.2 and 260.1 (YT Radical MP) I actually found YT radical MP more stable as well.
But listen that all matters what weight setup are you talking about lead up tgk 260.2 like berdych and it will be THE most stable thing around providing you can swing that thing for more than 20 min.
Pro stock is not magic IMHO it just allows for greater freedom to customize to your exact preference. since radicals are already pretty light in stock form I would not spend a penny on 260.xxx now if you need an extended length than by all means pro stock is the only way to go
"HarTru easy on your joints but hard on patience..." -badcall