keybladestyle:
Best thing would be to have your SO handle your Sirupati to get a sense of what length and weight (and handle size) would be best for him. Any of your listed models in the 15"-18" length range would work well, but unless he's a really big guy, weight is a consideration.
If you want the new knife to be a surprise gift, just leave your Sirupati lying where he can pick it up, maybe have him chop something for you and watch his reactions.
Of the models on your list, I think the WWII usually runs a little lighter for a given length.