I have camped twice this summer for a week each time with electric only sites. The first time I used an 18 gallon 2 wheel tote from out tent camper days. it worked fine, but I had to tow it when I needed to dump. I found a 1st generation Thetford 4 wheel, 35 gallon tank on Craigslist for half price and picked that up for our second week at a state park. It, too, worked well and allowed me to pull it like a wagon (by hand) to the dump station. I even used it for the good stuff (black water) half way through the week as an experiment that thankfully worked out equally well.
In these adventures, I learned a couple of things. A 35 gallon tank is BIG! Travelling, I stored it in the back of our van, but it takes up a LOT of space and while it's not that heavy when empty, it is bulky and a bit awkward.
A 35 gallon tank is HEAVY when full, over 280 pounds. I could pull it fine on the road, but in the dirt near the rig, it was a handful. I am 6'2" and a smaller person might need to think carefully about how they will move a full tank. As one poster suggested, they use a macerator pump to fill the tank in the bed of their pickup, so that is one way. if you know in advance you will always tow the tank, a 2 wheel tank is lighter and less expensive, but you need to think in advance how you will move it to the back of your TV, just as with a 4 wheel tank.
Emptying the tank: The Barkers are attractive because they have that side valve for emptying. You do have to carry & attach a hose, Etc. and store it somewhere-doable, but you have to think about it. The Thetford has the integral hose and it worked well for my use. I did not have to think about carry anything while walking from the trailer to the dump station.
Wheels: Depends on the ground surface you'll be on. I like the solid tires on the Thetford and they worked well for me. The pneumatic tires on the Barker are attractive, it just depends on what you think will work for you.
SF Bay Area
'99 Ford E350 V10
'16 Rockwood 8329SS