If you can afford it get the shorter jar for convenience. Otherwise the 5200 is perfectly fine.

Go with the shorter jar. It'll fit under the cabinet, it's quieter and I bet it's easier to scoop stuff out of than the taller one.

There is the 6300 model on sale at Costco for $469 till 24th. Do you recommend the 6300 vs 5200? Or is it best to go wtih 7500 (or 750) and the shorter jar which is the newer model?

We just got the professional 750. It's awesome. Around $600 or so...have to ask DW.

There are a bunch of different models... Some are identical, and some have significant differences. Here's a page that describes the differences: http://joyofblending.com/which-vitamix-to-buy

We bought a reconditioned 7500 and we've been extremely happy with it.

Costco has a couple. But the 5200S is on a great sale now: $349. I paid $500 two years ago.
They are all so powerful that I don't think the model number really matters.

I am planning on buying a Vitamix. Can anyone give tips on which model to buy and any big differences? I know there is a price range due to the different models and was going to look at Costco but I assume they only sell one model number.

Thanks!