Which lens do you recommend?

Would you get a 70-300IS for just under $500 new or the 75-300IS from the Canon Rep that he used just to show and it look like new for around $260.00

Thanks for the advice

Neither. I'd wait atleast till June when Canon announces a solution to the softness in verticle mode at 300mm problem with the 70-300IS. The 75-300 IS is an older design that has been replaced by the 70-300IS. It is really soft beyond 200mm and has lots of CA and lacks a bit of contrast.
You want a cheap 70-300, consider the Sigma 70-300 or maybe the Canon 70-200l f4, not cheap, but a good lens and a bargain L lens.

70-200f4L

Another vote for the 70-200 f/4 - it's a gorgeous lens, superb build, great IQ and very handleable. I don't miss the extra 100mm, and if I did I'd get a TC.
The 200-300mm range was the least used on my 75-300 II non-IS lens.
I'd strongly recommend this lens over a 300mm one, and the 70-300 IS while optically better than its earlier brethren, is still a pretty expensive lens. Bear in mind the portrait issue hasn't been resolved yet.
The old IS lens your rep is selling is not as good as the new version in terms of IQ. so save your money and get something better, you'll be glad you did.

you want 300, go with Sigma's 100-300 f/4. It's a little more, but it will give you a quality, sharp lens at f/4(without any TC's involved).

Between the 2, I'd go for the newer 70-300 IS. A much better lens all around. That being said, you might want to hold off for a little while until Canon finally gets the handle on the portrait issue with the 70-300.

Thanks guys.

Seriously ? Get the good-as-new 75-300IS ,sell it on Epay for a quick profit then buy the 70-300IS