Rich it depends I like the comfort and privacy of my own toilet. If I'm out and about in the RV park and I gotta go then I will stop in and use the restroom. But if I'm in my coach I'll use my own toilet because privacy and comfort is a major key as to why I travel in my coach.
Normally, we use our own. We bought it for the convenience and having it in-house is about as convenient as you can get. However, we generally have full hookups. If we have guests along they will generally use the campground showers so that it doesn't take all morning to filter through the bathroom one by one. Also, if boondocking at no hookup campsites we'll use what ever is available to stretch and conserve our water and holding tank capacities as much as possible. I don't think we'll ever wear out a toilet or sink so I don't really consider that an issue.
We use our bathroom right here in the MH. I personally do not like to use any public restroom anywhere unless really needed. And I stress REALLY NEEDED. It's not good to hold it but if the MH is parked right outside Walmart then I would rather go in the MH (our home) than Walmart any day! And because it is just the two of us, the tanks do not get full that quick and like Sean said we most of the time always have fullhook ups. When we stay at resorts the restrooms are very clean and very nice.