I would look at the pros and cons of both routes. Being 22 years old I have often contemplated that although I am an RN maybe I should sit for the MCATS and go to med school. However, during this time I realized that while med school sounds so attractive, what I really enjoy doing (minus the headaches, the scut work), is practice nursing.
Not to mention, while when you add together the years of undergrad, med school, residency....taking into account that the last 8 years you are pretty much not having any sort of life.... med school still is the longer, much more time consuming route. Residency, at least from I have seen involves a heck of a lot of scut work and at least during their ICU rotations, they are working 80-100 hours of week, on call every third night, post call til about 4-7pm, never ever sleep on their oncall nights. There are physically easier rotations and there are harder ones, but just remember after finishing four years of med school you are going to pretty much live in a hospital for four years making the equivalent of the janitors who put in 40 hour work weeks.
Personally, CRNA sounds much more attractive. It is the practice of nursing plus finally having some autonomy, the ability to focus entirely on your one patient for that OR experience, seems to be a great challange, intellectually stimulating, ya get to be the one who intubates, I could go on. Anyhow, as a 22 year old who grade wise could go either way, I personall am going for anethesia. I already have one year of ICU nursing down, but plan to stay for two more. When you add that onto 2.5 years of CRNA school, let's see... I will be 27.5 pretty much 28. Since I still have to take some prereqs and prepare for MCATs, it probably would be another 1-2 yeras before I could even apply, plus eight more years, I'd be a minimum of 33 when I finish. That is after incuring a heck of a lot more debt, not having any life (yes I realize that CRNA school is pretty much 2.5 years of no life...but it is not 8)
You need to decide where you find your niche and really what practice suits you best. Definitely try shadowing both, and not just one of each... if possible. Good luck.