The original Vaquero is larger than the New Vaquero. If you have large hands, you will most likely prefer the original version. I put oversized grips on a pair of my original Vaqueros, so you can tell my preference.
The hammer spur on the New Vaquero is lower, making it easier for the average shooter to work the action without shifting grip. I have no trouble at all working the original style hammer. The first time I tried to work a New Vaquero quickly, i wound up jamming the hammer spur into a joint on my thumb. Ouch.
I much prefer the originals, but I would appear to be in the minority. (Far closer to Hoss than Little Joe)
And the previous observation is spot-on. Ruger listened to the Cowboy community, and made major changes to their Vaquero. Now a bunch of us grumble about "newfangled".
I would buy the New Vaquero. But I miss the one revolver I did not have to re-work to make fit.