If money is a big factor, I'd try and grab the more recent releases that are still floating around so you can get them close to their retail price. There was a link posted just yesterday to HLJ with additional VF-19 Advance stock (now sold out, unfortunately). Looking at your list, I'd say Isamu's VF-19 or Rod's YF-29.
The ones that have been out of production for awhile are generally going to be well above retail, and they'll still be above retail in a few weeks or months. Only exception would be Brera's VF-27; I've been able to find those at around its original retail price, so that might be a good choice too.
But honestly, it comes down to which you like best. Five of your choices are YF-29s, and they're all the same aside from paint schemes and a different head unit, so it really does come down to personal preference and what you can afford.
If I was in your shoes, I'd get the VF-19. As far as Frontier valkyries go, it's a beautiful and unique unit, especially if you don't have a YF-19 already.