We have the big Thetford tank... I think it's 35 gallons. We've had it for about 5 years. It works great when needed. We dump both black & grey water in ours and store it under our camper on a platform we added. It goes everywhere we go. ;)
As for the Barker... I think it has a side dump valve which would be nice, but then you have to carry the hose with you (as others noted). It's a trade off I guess... both will surely do the job equally as well.
Happy Camping!
John.