Hi and congrats on getting into motorcycling! My first bike, besides a few scooters, was a '99 GS500e - basically the same as the GS500F w/o the fairing. It was/is a great first bike. Light weight, nice riding position, easy maintenance and enough power to get you going. I used it as a daily commuter and weekend ride, putting about 22,000 miles on it in 4 years. Now, I rarely rode in temps over 85 F, usually at lower elevations and I was more a cruiser than a racer, but I never had any issues with the engine being air-cooled and carbureted. The GS engine has been around for, what, 10-15 years? So you can expect it to be quite reliable. The rest of the bike has proven as well made - other than damage from vandalism, I've never needed any repairs beyond the normal oil change/chain cleaning/tire replacement.
That said, I have had my '05 SV650 for a week now and love it. Although the riding position is similar, it is a very different bike from the GS500, mainly due to the engine and the frame/suspension.
The SV has a much more responsive throttle - it is downright twitchy compared to the GS. Throttle control is more difficult on the SV, which could get a brand new biker into trouble if they don't take it easy to start with. Engine braking on the SV is far more pronounced. The SV has more power, and torque, at every RPM than the GS, which makes it easier to get up to speed if you miss a downshift. The SV also feels more stable through turns, both fast and slow speed. It handles normal bumps in the road better both on the city streets and freeway.
If the SV had been available when I bought my GS, I would likely have gone with that instead. However, I do think that the GS is an easier, more forgiving, bike to really learn how to ride in all situations and get experience with and I've had a great time with mine.
Which ever you go with, you'll still end up having a smile on your face when you drive away from the dealer

Enjoy!
oh yah, be sure to get some good riding gear as well - comfortable, safe equipment will have as much impact on your fun as the bike. Nothing worse than a helmet too small or gloves too big.