HA bows:
Nomad bow -----> Not my first choice, very little damage, BUT, if you want it, it will alow you to have a build with Horser Archery 5, not that bad if you can manage those headshots (10wn will sure help you) - I do not recomend this build as first build.
Tatar Bow -----> Since you cannot get a good build with HA5 with this bow, I'd skip it unless you want the looks or a hybrid build and are missing skill points somewhere else.
Horn Bow ----> my bow of choice, good accuracy, best missile speed on horseback, can get HA4 at level 30 ----> you can even go hybrid and spend some points in PS and still get HA4 at higher levels. Although HA3 will do just fine too.
Yumi bow ----> More damage than horn bow, better accuracy, best reload in game, WORST misile speed in game. Its a nice looking bow, but even with PD6 I would still use the horn bow. Although a loomed yumi will do fine imo. With a yumi bow you will be locked to HA3 for most of your gaming life.
I'd say Horn bow is the best for my money.