I vary the bows some. I love fast magical shortbows for pvm, but really any bow with 30-40 ssi does well. For Pvp, they have a variety of bows they like which have good pvp specials on them (heavy xbows, etc).
The trouble is, you won't get exceptional all the time with all those due to the difficulty level. A regular bow is nice because you'll get the exceptional bonus all the time, but then again, if you roll a damage mod on the bow, you'll get pretty high damage increase anyway.
Maybe make a bunch of different types. I made 5 magical shortbows, 5 heavy xbows, and 5 regular bows on my last kit. Got a nice pvp heavy xbow out of it, so broke even, but only had the 1 nice bow.
Always use Ash for bows, the main mod on bows is SSI. Since most bows are slow, and the majority of them are VERY slow, ssi is the main mod you want on any bow. Enhancing bows depends on the mods already on it, but when you create them, you want ssi, ssi, ssi.
Always make the bow with ash, don't make it regular and try and enhance later. The only people who do this are those with dozens of kits who can afford to waste money. Most people can't. Just make them with ash, there are plenty of other ways to get DI and HCI.