I had a Bailey 15" machine on a frame and didn't enjoy quilting on it. I will say that there is a learning curve no matter what way you quilt. I free motioned nicely on my sit down machine and did nicely with the frame set up but just did not enjoy it - and it's a huge floor space waster. I now have a Tin Lizzie sit down and love it. I have oodles of space and I quilted an oversized queen on it in less than 5 hours while practicing my feathers. love, love love my Lizzie.
I suggest before you buy a longarm, look for a longarm class nearby - especially if you can get a one on one class instead of in a group. If you take a class in a group you will not get to use the longarm nearly as long as if you were one on one... Ask the teacher to skip the maintenance part of the class and just dig in to the quilting. I know that our local class is like 5 hours long and one hour is on maintenance alone.. and the teacher only teaches if she has 5 students so doing the math... you don't get very much hands on time - which is why I didn't take her class... there are others out there though if you find it.
If you enjoy the longarming after taking the class, then start to look for one that will suit your needs
Once you decide you really want to go for it then I'd suggest going to a quilt show that has all of the vendors under one roof and trying every single machine so you can compare... then you can decided if you want to go new or trade in or Craigslist. People sell their long or midarm sets ups when they downsize(like I did and I don't regret it one bit) and when they upsize... you can get a great set up for a lot cheaper if you bide your time and keep an eye on the sales (and check the local dealers for trade ins as well)
Best of luck on your decision