I now have a vertical front load charcoal fired (GOSM gasser converted to charcoal), and the SNP 40". The small verticles work great for butts, picnics, chuckies and the likes, and are fuel misers. If you plan on doing ribs, a full slab won't fit in most verticals, except a 22" drum or WSM, or wide body/big block. The horizontals use more fuel, yes, but the added convenience of the sfb, grate size and access to the cooking grate is nice for the big slabs of meat.
It really comes down to preference, and that is what you should ultimately base your decision on. If fuel useage is your biggest concern, go with a verticle, if it doesn't matter, but grate size does, go horizontal. If you don't have the cash, go the cheaper route first, then upgrade later.
Good luck and great smokes to ya!