The buses at the Settlement Depot (near Pioneer Hall) go to Disney Hollywood Studios and Wilderness Lodge (and then MK). For all other Destinations you take internal buses to the Outpost Depot. I prefer to take the launch to get to MK (or WL or CR), it is much more in keeping with the laid-back FW feel than hopping a bus. I don't mind taking the bus to Epcot or Studios, it's not that long a trip. I hate taking the bus to AK or Downtown Disney. AK is just a LONG ride. And DD buses seem to pick up from a bunch of other resorts before heading to DD. So, if I had a car I'd definitely use it for those destinations. Well, I have dogs in the motorhome, so I would drive everywhere so I could do mid-day breaks as quickly as possible, but that's me, and I don't tow. As far as the convenience of the buses, even in low season late at night I can't recall waiting more than 20 minutes for an internal bus, and maybe 30 minutes for the DD bus.
Hope it helps.