A professor matches my previous research and the other matches my interest. Which one should I choose?
Ultimately, I would choose to work on what I'm interested in rather than what I have experience in, assuming that you have enough background to follow your interests (but in a 7 year PhD program, you'll have time to learn the techniques you'll need) and that there is a future for you after completing the program.

(Learning how to use capital letters and to punctuate your sentences properly will also help in the future.)