Defintely get the Bridgestone. It's not a singlespeed. One can see both deraileurs clearly in the picture. Forget the Schwinn...it's got a one piece crank which means it was a lower end roadbike for it's day. Don't fully agree about replacing the saddle as it looks serviceable enough for a 16 mi rt commute. Money better used in getting new tires. Mtb specific street tires come in widths as narrow as 1.5". That'll give you less rolling resistance. The knobbies will have to go as they really slow one down on asphalt. You'll want to get Mr. Tuffy tire liners as well to reduce your flat rate. Fenders, rack, frame-pump, tire levers, multi-tool, chaintool, lights, etc. for a safe, enjoyable commute.

http://www.bikeisland.com has everything I mentioned about accessories at very reasonable prices w/no shipping or taxes. You'll have your stuff in 3-4 days. Would recommend the Park MTB-3 multi tool(it includes a chaintool), Topeak Road Morph w/gauge frame-pump(it's like a miniture floor pump), Planet Bike fenders, etc. Did a price check for a complete commuting accessory buy and everything came in at under 350.00, including extra tubes and great tires. If you're interested PM me and I'll send you list of what I picked out. I've got an mtb that's being set up for commuting, so it was like a dry run for me.