Kevin I have a 2 wheel 10 gallon tote that I bought in case of emergency. First time out with our Kiwi the kids and their friends had fun flushing the toilet. Luckily a fellow club member had one I could borrow. I found it on sale at a nearby RV store and picked it up. Haven't needed it since that first time. But I have it strapped to my bumper and spare tire for safety. As for which is best, that's up to you and your needs. Holding nearly 60 gallons of waste water I can't see a huge need for one other than to help in an emergency. If I need to dump 60 gallons I think I'd hook up zip to the dump station then bring it back after a good flush.
We have not been out in the Outback for more then 3 days so far and that is about the limit we can go with out dumping. As soon as we plan a trip for more then 3 days I will go out and get one of these. A buddy of mine has the 4-wheeler model with and that's the one I will go with when I do get one.
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