Bansko is about 2km from south ( lift) to north, and is built on a slope south up and north down
If you are in the north you will have a bit of a walk up hill to the lift.
If you are south you will be right next to lift, but when you have had a few ; you will have a walk back up the slope to your digs.
I recommend mid to south. The nightlife is smack in the middle.
The town centre is about 1km North (downhill) of the gondola. If you are planning to walk to the gondola (Along Pirin Street which can be nice if not too heavy snow), then you really need to rent a locker at the gondola to store your skis/boots/poles. It would be too far to walk in boots and carry equipment. The walk uphill to the gondola each morning (in suitable footwear) could be a great warmup exercise before you hit the slopes!