A bit of both for me. I like the Bastard Sword for it's dual-capabilities, pretty much one of the strongest one-handed weapons I think, isn't it? Though I suppose it is outdone by dedicated two-handed weapons like my other favourite, Heavy Great Long Bardiche! Longer reach on horseback is obviously better, but I used a Nordic Short War Sword for ages, mounted or no, it still did what it was supposed to...
Never been one for short swords, but after reading Bernard Cornwell's Saxon Series, with Uhtred's raving of short swords in a tight melee, I decided to go that way... It works. Quite often my bastard sword just bounces around uselessly.