You will get lots of opinions on carburetors.
In the one-barrel variety, there are:
Carter YF (W-1's and WA-1's for multiple carbs).
Holley 1904, 1908, and 1920
Rochester B series
Stromberg B series
Zenith 28 and 228 series
In the four-barrel variety, there are:
Carter 400
Holley 390
I personally go with the ABC's of carburetion: (A)lways (B)uy (C)arter. Others will have differing opinions. I like multiple carbs. 2 Carter W-1's on the 250 would be mighty difficult to beat.
Hot water heat is OK, but MAKE SURE TO SWITCH THE ANTIFREEZE ANNUALLY!!!!! Those electrolysis bugs get hungry!
Another option to exhaust and hot water heat to the manifold is to use a sheet metal heat stove on the exhaust manifold forcing the inlet air to pass through the stove. May not look as neat, but does help to better mix the air and fuel, as well as controlling icing.
Regardless of which carb or carbs you use, if at all possible, avoid using adapters. Buy carbs that fit the manifold.
While each brand has its disadvantages (some actually have advantages!); in the long run, most enthusiasts will be best served by purchasing a brand with which they are personally familiar, or wish to become familiar - or keep it stock. Unless the manufacturer makes a model SPECIFICALLY for your engine/transmission combination, than ALL aftermarket carbs will require something (recalibration, different fuel lines, different linkage, different air cleaners, all of the above, etc.).
Jon.
