Nuclear medicine is a neat field, and can pay well. You also get to play with some neat kit and kick Cancer's ass. You will also lose patients and have to have the strength of character to not let that fact impact your patient care. Looks like the jobs advertised for the techs, not the MDs mind you, are 50-100K a year depending on market. Keep that in mind.

Basic Science research is what you do for the love of it. It pays shit, you are at the whims of grants and funding and politics, the hours are long, tons of paperwork, you have to publish multiple articles etc so you can prove what you are doing is worth the hassle and there is no prestige unless you discover something. Saying that, I've met people in basic research and they would all do what they do for free (and some earn so little they might as well be).

I've met MDs who were sad and depressed, but so far I have not met any basic researchers who wish they were doing anything else. The key here is what is going to get you out of bed in the morning? what is going to keep you up until 4AM reading a tech journal because you LOVE this stuff. If you find a passion, and you have a talent, go that route. If it was me? I'd probably go the basic research route and use that to get contacts, experience, etc. Then you can always go back and get the MD/tech stuff since you will know more about how the equipment works than anyone else in the hospital.

Nobody can answer this but you as you are the one who has to live with the decisions. My word of advise is to take the path that does not limit your options in 4-5 years. There are people on this board who have had 4,5, 6 careers. Nobody knows where your life will be in 10 years, so don't limit options if you don't have to.

One thing I may suggest is to let the other people know what you are doing and keep in contact with them on good terms. This is a problem I have had all my life so if you can not be like me you will be one step ahead of the game.

Its late and this is a ramble, but hope it helps.