Feel of the Harmonica
Each model of harmonica uses slightly different dimensions for length, height, depth and hole spacing (as well as the size of the holes... this is mostly a factor of how thick the walls of the comb are). How the reed plate, comb and cover plates meet also affect its feel. The Special 20 for example uses inset reed plates and the Marine Band uses sandwiched reed plates (sits directly on the comb). The beveled edges (if any) of the teeth of the comb also affects how it feels (Marine Band has none, while the Marine Band Deluxe has a slight bevel). Some players like a larger harmonica and some like a smaller harmonica (Marine Band is the smallest... which makes it easier to cup). Some harmonicas use tabbed (vented and non-vented) cover plates while others fully wrap around (see Harp Tech Studies #1). With all this said, experiment with different models until you find the right one that feels good to you. Of course the playability is the most important, but these are aspects to consider. I personally feel the Hohner Crossover is the best model on the market today for feel, playability and sound.