Where would you even get a VF-25S from at a reasonable price? I've got a VF-19 Advance and absolutely love it, but a VF-25S would be the one Frontier Valk I'd hanker for, and have had no luck finding at a decent price.
But you really can't go wrong with either. The VF-19 is a must have in my opinion because it has that modernized design, yet still a classic look.