My favorite is PolyScale acrylics. Unfortunately the nearest hobby shop that carries them is about 35 miles away. The local Hungates chain store carries the Testor's Acryl line; if I need a jar in a hurry that's what I'll buy. But I like the texture of PolyScale better.
Maybe I should clarify that I'm primarily a ship modeler, and I don't use an airbrush much. I like the brushing consistency and finished appearance of PolyScale. Testor's Acryl is ok, but to me it seems a little syrupy by comparison.
I've also used Model Shipways acrylics quite a bit. I've had mixed success with them. Some of the individual colors work fine; they handle just about like PolyScale. Others - expecially the blue shades - have given me nothing but trouble. They refuse to mix up into a nice, brushable, opaque consistency. (It's possible I got a bad batch, or that they've been sitting in my shop too long.) Anyway, MS offers some colors mixed especially for sailing ships that aren't available elsewhere.
Testor's Acryl recently added a good range of ship colors. They seem to be the same colors that used to be available in the Floquil "Nautical Colors" line - which is now defunct. The nearest hobby shop that carries this particular series within the Testor's line is more than 100 miles away. Ouch.
I grew up with enamel model paints; my memories go back to Ulrich, Pactra, and Scalecoat. I bought my first water-based paints in the mid-seventies, when I was working my way through college in a hobby shop. It stocked the old PolyS latex line (which I still think was the best ever). Initially I had trouble getting them to cover adequately, but I quickly figured out that brushing water-based paint takes a different technique than brushing enamels. I got permanently hooked on acrylics when I noticed that my modeling sessions were lasting five or six hours, where I'd previously felt like taking a break after two or three. The reason: the smell of the enamel paint had been giving me mild headaches without my knowing it.
I still use enamels sometimes. I have yet, for instance, to find an acrylic gold or silver that can top the best of the enamels. But with those exceptions I'm a thorough convert to acrylics.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.