the warranties look better and they do have good reputations, at least on the internet.
Good luck; there is a 95% chance that a computer is not prepared properly for sale. You will wind up with something you cannot use because the previous owner did not follow the steps in the instructions I linked to. You will have no choice but to return it and hope to get a refund. I bought a Mini many years ago - it was supposed to be "like new"; instead, it was filthy and unusable - registered to the original owner. I got my money back, but I was lucky.
Unless the warranty is from Apple, it'll be pretty much worthess.
I will never buy any electronics on ebay again. And I would NEVER trust any claims about anything online unless I can get it in writing from a reputable manufacturer.
But, you've now gotten pretty much the same advice from several contributors here, and will still buy it from questionable sites, so good luck!