A professor matches my previous research and the other matches my interest. Which one should I choose? I am a fresh PhD student and I need to choose an advisor to guide my research. Currently I find it difficult to choose. 

One professor's current project pretty well matches my previous research experience. Although I would not say I am interested in it, at least I don't hate it. But I find most of his students will need 7 years to graduate the PhD program under his advisement. The speed of this professor's life is really slow. The most important thing is that he rarely gives his students constructive suggestions when they confront problems in the research. I know a PhD needs to have the ability to conduct experiments independently, but some kind of guidance is necessary.

As for the other professor, his project is really exciting and he published many papers with high impact factors. It is not that related to my previous experience but it may use some of the techniques I used before. I like it but some of my friends told me this professor is really picky and tough. With him as an advisor it may be difficult to get job after graduation. 

Currently I am working with the first professor. I try my best to make myself get interested in the work, but I am still hesitant.

What advisor should I choose to achieve a satisfying research experience?
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.)