Okay, first a quick comparison:
Dell Latitude E6500
1. Business grade laptop (durability)
2. 3 year warranty
3. Starting from 5.2lbs
4. eSATA port (not sure if you'll use this)
1. Windows Home Basic
2. Smaller 160GB HDD
3. 15.4" @ 1280x800
Sony VAIO VGN-FW292
1. 16.4" screen @ 1600x900
2. larger and probably slightly faster 250GB HDD
3. Vista Home Premium
4. Wireless-N Support
2. 1 year warranty
First of all, both will be fine for recording music. (just make sure you get a good digital audio interface device and proper sound equipment. )
The Latitude is a business grade laptop and it comes with a 3 year warranty. If durability is a priority, go for the Dell.
Other than that, the Sony seems better for multimedia. Larger hard drive/larger screen with higher resolution(better for multi-track editing), HDMI-out.... the only thing is weight. The Sony weighs at least a pound more than the Dell.
Pricewise, Dell periodically sets their price up and down so eventually there's a low point you can grab... I'm not sure if the current savings is the lowest.
As for the Sony, normally it's cheaper to purchase from 3rd party retailers but that particular model still seems new as I can't find them elsewhere. If you have time to sit on it, wait and it should show up at a lower price elsewhere.
Hope this helps.