I own 2 Eagle Talon TSi AWD's (Eclipse GSX), so my opinion may be a bit biased. However I will provide more than just "3000GT will smoke it" like that smart guy above.

First off, If the cars are automatics, I wouldn't buy either.The 3000GT SL, is kind of the midrange model, more luxurious than the base but less performance oriented than the VR-4. The Eclipse GST is pretty much top of the line for the Eclipse, minus the GSX's AWD. The 3KGTSL has a nonturbo DOHC Mitsubishi 6G72 making 225 horsepower. The GST has a Mitsu 4G63Turbo making 210 HP. Now, you're probably telling yourself "Sweet, the 3KGT has more power it's faster." You would be wrong. The 3KGTSL weighs somewhere around 3500lbs., but the GST is only just around 3000. The 3GT only has 15hp more hp to carry around an extra quarter of a ton. It would be like driving a GST with Rosie O'Donell in the passenger seat. No, the SL would not smoke the GST, however a 3000GT VR4 would smoke the GST hands down, as long as both were stock.The GST, or DSMs as i'll call it, lack of reliability is often over exagerated. A lot of them get the shit beat out of them by kids who mod the hell out of them and wait for them to blow up instead of performing preventative maintenance. Just take good care of it. In reality the GST will be cheaper and easier to maintain/work on than any 3KGT, it will also be a lot easier to find used parts as there are MANY more DSM's than 3KGTs/Stealths around. The DSM also has a MUCH larger following than the 3KGT crowd. For every one knowledgeable 3KGT guy you find, you'll find another 10 Knowledgeable DSM guys. It's real easy to find people who know them and can help you out with them.It also depends on what you want to do with the car, -if you're just getting a car to drive around. The 3000gt has more room and runs on regular gas, while the GST has a not so big trunk and runs only on premium. However, I'm pretty sure the GST does better on MPG. -If looks is your bag, either car is good as there is a wide array of gay ugly gaudy body kits available for each car along with other crap. -Lastly if going fast is what you want, the GST takes the cake. Your options for making a 3000GT SL faster are very limited without spending a good amount of money. You can turbo the 6G72 or drop in the twin turbo motor from the VR4/Stealth R/T TT. However, the GST is already turbo, and for the price you spend on a twin turbo 3KGT motor you could fill your garage with spare motors for a GST. Also, because turbo DSMs are so popular to mod, aftermarket performance parts are a lot cheaper. Hell, I just put a full 3" exhaust on one of my Talons, that I ordered in 2 seperate pieces (downpipe/catback) from ebay and spent less than $400 INCLUDING shipping. The quality was also amazing, the welds were excellent, and it hung perfectly. You can also get bigger turbos for around $600. There is about 100 times more potential for the DSM. People have spent less than $1000 and run 13's in the quarter mile with turbo DSM's. The same CAN'T be said for non-turbo 3000GT's.Check out these links.3si.org and dsmtuners.com for more info.Hope it helps.