A lot of the answer depends on the type of quilting you plan to do, your budget, and the space you have available. Renae Haddadin wrote an excellent article on shopping for a longarm (she eventually chose Innova) and you can find it here -
http://www.quiltsonthecorner.com/inc/sdetail/1349. You have to put the article in your shopping cart (at zero cost) to receive it. Good luck with your purchase. Like Renae, I decided on the Innova, but I got the 26" on a 12' frame before the lightning stitch was available, and I am very happy with it.