I've run the gauntlet of banner creation so I'll chime in here.
My first banner was done at Fast Signs, and while they did a great job and were impressed that I showed up with a print ready illustrator file in hand, the banner was on a plastic coated paper rather than vinyl which sucked. It had grommets and all and worked for one show, but I scrapped it after that and decided to do vinyl. The cost was decent, the turn around was same day, and I was pleased because it was more or less a last minute thing and I needed it fast.
Shift a year down the road and I'd moved hell and gone from anything close to a real city. I once again needed a banner. So I looked around, didn't feel like the 1.5 hour drive into Houston, and went with a local print shop. It took them six days to do a job they quoted for 3. When it was done what I had was great for a yard sign type thing, but sucked ass for conventions. It was...horrible. We ended up hot gluing velcro to the back of it to even get it to look halfway decent and we went with it because at that point we had no other choice. If it weren't for my wife and her craft skills I'd have been well and truly screwed. (Thanks honey!) Cost wise it was more for the vinyl than the Fast Signs version, and I liked it even less. Plus the people there acted like I owed them something and should be GLAD they got it done in 6 days even though they said 3. Note to self, NEVER tell them when you need it by, because they'll stretch it out whenever possible. You need it yesterday!
So, another year gone by and I'm freakin serious now. I want something long term, and awesome looking. I saw a guy's table set up at a con and immediately knew I wanted to fully rip off his idea fromt he ground up. So I just walked up and said "Hey I like your table banner, where did you get it, I'm about to copy you!" He laughed and gave me a website and we were best buds after that. Turns out I didn't go with the folks he got his from, but from another even less expensive place that does similar work. What I've got now is a fully silkscreen printed 4 color logo on an 8 foot table throw that can be used all the way down to a 4 foot table. It's washable, color fast, and that thing looks AMAZING! I haven't set it up at a show yet since all our shows this year are later in the season due to my soon to be born son coming right in the middle of con season! (I still say he did this on purpose but my wife's lobbying heavily on his unborn behalf.) When I set it up I'll take pictures and post em up, but trust me when I tell you, this thing looks bad ass! Cost wise, it was a good bit more expensive than either of the banners I bought before, but by the time you factor in what I spent on both of them, I paid less for the table throw and I got an infinitely better product. Plus, I can still use the not so pleasing vinyl banner elsewhere so it's not a total waste like the paper one was.
The moral of my story is, pony up and buy for the long term. You'll be happier.