Hmm, I can't answer all your questions. As far as size goes, get one big enough so people sitting at the table are actually under the umbrella. Make sure you get one that has a hand crank to open or close it. The kind where you push it up and insert a pin in the pole are a real PITA. Mine also tilts which is a nice though not always necessary feature. Sunbrella is a good fabric. You want a fabric that will resist fading and rotting.

I bought one of these two years ago from Costco online. The store didn't seem to carry this particular size/quality and it was great to have it delivered so I didn't have to wrestle it home. I also bought the base (separately priced). Both are really good quality and I've been more than happy with them. I like the tilt feature, as I use it to keep the sun off my red headed grandbaby when he's playing in my yard - tilting it offers more coverage when the sun moves, without me having to move the umbrella. It's HEAVY!
costco umbrella

We got ours from Home Depot, also a tilt, not as heavy as the Costco but still a good product. We also ordered a second one for an additional table in our yard from Amazon, and are equally happy with it, again not as heavy but it has the tilt feature and does what it's supposed to.

We have a very nice umbrella from Ace Hardware that was somewhere between $50 - $100. We try to store it in the garage during heavy rains.

I agree that you should get one that cranks. I have 2 that crank and 1 with the pin, and I can barely reach the pin. I would also get one with a vent, as it doesn't take a big gust to get under the umbrella and lift it. Ask me how I know!

agree to get a crank umbrella. I think 9' round is fine for a rectangular table, tho probably won't shield everyone from the sun all the time...

I have had a couple from home depot which were ok, but not great... I have a couple from frontgate now which are great, but I bought them at end of season clearance sale a couple of years ago- wouldn't pay full price.

I also had a smaller (6 or 7') umbrella which I had for many yrs- so long that I don't remember where I got it, but it was inexpensive, crank with a metal pole- probably bought it at a home depot/target type of store and it held up unbelievably well and we weren't careful with it and it was in a couple of windy areas at a couple of our homes... so doesn't have to be expensive to be good quality!

thank you everyone! I'm off to Costco at lunch today so I'll see what's in stock locally and order online if needed.