The bottom line really is it has to be the best one for you. I personally feel there is no better turbine in the world than AMT, but I'm willing to deal with the bigger size and heavier weight in order to get the huge service intervals and the fact that they never wear out. Most people however want compact and light. That's fine and I am the only guy in my area that flies AMT so I need to be my own expert with those engines. If this is your first turbine the BEST turbine will be the one that the majority of jet modelers in your area already fly so that if you have any issues at least you have a support group to help you with any issues. The best turbine doesn't necessarily have the best price, best warranty, best Power to Weight ratio etc, the best turbine is the one that will work for you with the least headaches. There are a couple manufactures I wouldn't fly if the engines were given to me but I suppose that is due to my personal experiences either with the physical engines or with the company themselves.
At the end of the day, I had success with my first engines (RAM750's) because there was great support more or less locally that I could turn to.