I've worked with Vallejo, Humbrel, Life Color, Model Master, Testor's, Pactra, Scalecoat, AK Interactive, Mission Models, and Tamiya. Of all of these, I keep coming back to Tamiya. It just works better. Vallejo dries too slowly and Mission Models needs to have acrylic binder added or else all you're spraying is pigment. Matching Olive Drab is near impossible. I don't believe their actually is one Olive Drab. It never existed.
A recent problem was using Mission Model Dark Ghost Gray for equipment on the New Jersey Engine Room. I ran out and bought more. I swear, the batch is different. It has a distinct purple overtone and when painted next to the original and it was awful. It's also fragile after drying. I just ended up mixing Tamiya Neutral Gray with about 20% Tamiya Gloss White and the color is now uniform and perfect. I've been using Tamiya paints since they came on the market and keep going back to them. It's not for want of trying. Life color is pretty good too and they had a very nice updated USN Haze Gray. It airbrushes and hand brushes nicely. It's not that easy to locate.