Larger front to back than side to side (saved counterspace), large second side (big enough to wash things). Stainless steel is wonderful! It will last you for years. Just get a good quality one (pay extra for that insulation and the thicker gauge).
Best advice--get two (yes, two) garbage disposers so you won't have to pick a side when peeling or soaking. If you only get one disposer, put it in the larger side so you'll have the convenience after soaking roasting pans and washing pots. You can always aim for the disposer side when you're peeling vegetables and scraping dishes. We have two disposers (each switch is on the side of the sink for that disposer). Two people work very conveniently at that sink when necessary--they control their own messes. Also, I don't have to dig out a mess and put it in the other side to use the disposer--I just flip the switch for that side. One caveat--use each side now and then so they don't get clogged or seize up.