I've tried a few and this is my favorite one, the Maha MH-C490F 4 bank smart charger. This one can charge 7.2v, 8.4v, and 9.6v cells which some of the other ones can't. It also does so pretty quickly.
Also, of the 9v cells I've tried, only the Maha ones are still running for me. My plainviews don't work anymore, with a relatively short life. My ipowerus instant burst also sucked pretty bad. One was unable to charge on arrival. It's replacement worked but got worse and worse pretty fast. Now, all 3 of them that I have are detected as bad on my charger and won't charge. It's been less than a year. The 2 maha 9.6v which I got at the same time is still working great, with much better capacity (runtime at least) than any of my other cells, and have never failed to charge.