Personally I think Tea Kim's is a VERY good site. I have Learned VERY much from that site. But of course, Genki is good as well. I think it depends on the person and how someone likes to learn. What I like about Tea kim's site is the way he explains the grammar, I personally thinks is the best way of explaining, and I have tried many other sites and book. Haha. Good luck with learning ! （頑張って！）

I used Genki in university, but I think it helps to learn from various sources.

choose both two are better than one :)