The GTS will be better at high resolutions, but I think the GTS is easily worth the extra over the GT for the better cooling.
I'd go for the GTS in your situation!
Sony NEC Optiarc 20X DVD±R DVD Burner Black IDE Model AD-7190A - OEM Item #: N82E16827118003 Return Policy: Standard Return Policy $23.99
I'd stay away from NEC DVDRW drives. I once loved them, till I found out that at some time along their lives there's a substantial chance for the drive to stop reading burned DVD-R media. BTW, many people share this issue with NED DVDRW drives. I've heard about 3500, 3520 and 3540 drives going crazy like that, and there's no solution from NEC.
I've had enough of that and got a SATA Pioneer DVR-212 and it's PERFECT! VERY high burning quality and no known issues.
Regarding the GT/GTS dilema...for a $30 difference I'd go for the GTS.
The GTS has 3 advatages:
1. Higher clock rates = higher performance
2. Higher amount of Stream Processors (128 in the GTS vs. 112 in the GT) = higher performance
3. Better cooling = better stability and higher possible OC.