Let's see if I can help here. All three are nice & good choices and you might want to purchase all three...
COMBAT MASTER. This generally doesn't come with the amount of work curving the holster as much. The tan finish may not be as costly, either, vs. the Havana Brown on the Concealable model. This comes with a larger 1.75" belt loop, which you may or may not need.
CONCEALABLE. This has more curvature built-in at the factory, which may account for a higher price. This also comes in a nice "Havana Brown" finish, besides black, which is nice. The belt loops are at 1.5", which may be all you need, I don't know. A very nice holster, I'd say near equal to any long-lead-time custom maker.
AVENGER. Also a classic straight-up design with no cant. Many holster makers offer this style, too. Galco, again, has a relatively high quality built into its products. You might find this one slightly easier to re-holster with that reinforced top lip. This holster also comes w/1.75" belt loops and should work well with any good, rigid, holster belt. I like the idea of that adjustable retention screw. Re-holstering is very important to me (as I'd have to be able to go into handcuffing mode quickly) so I'd choose this one out of the three.
For me, I'll usually use leather for the thumb-break, but my work exposes me to the public a bit more, on occasion. Mostly for open top work, I use Kydex/plastic/synthetic. Galco has great products and I can't see you being sorry with any of those choices you've already selected.