Mark, for what its worth I have tried several brands of primers on some of my recent builds and this is my opinion on them.
Vallejo - Nice finish, self leveling, clean up in tap water, fast drying, sctraches easily and cant be easily sanded. would recommend a respirator.
Stynylrez by Badger - Smooth finish, self leveling, shoot at higher pressure, clean up in tap water, fast drying, easily sanded when cured, very low odour. NOTE: Dont leave in airbrush cup for any length of time as it is very hard to remove once dry, in other words you can ruin a good AB.
Mr Paint Primer - Very smooth finish, self leveling, shoot at lower pressure, clean up with lacquer thinners, easily sanaded when cured, very strong organic odour - respirator required or paint booth extraction or both.
My personal preference is Stynlrez due to its finish, sandability, clean up and low odour and general ease of use. I have heard cases of the product going bad in the bottle, but I have had mine for almost 2 years and havent had any issues, just give it a good shake before ever use.
I hope this in some way helps.