I would blend with a Tok'ra. Thousands of years of knowledge and experience, longevity and health, and still retain relative autonomy. Even if I'm only in control 10% of the time, with how long the lifespan is I would still experience far more life with perfect health than I could without a symbiote.
I don't think I would want to be blended. Not even with a Tok'ra. Though, the Jaffa deal might be more acceptable. You still get a long life without disease, and no snake up your head. You would have to change it once in a while, and get some Kelno'reem going every night, but that's a small price to pay. Certainly a better deal than being used as puppet for good or evil.
Maybe Tok'Ra but I would want to know them first and get along to begin with. That being said I would likely be ok with it being done all of a sudden to save my life. I mean I would be dead instead then and the tokra by and large have been alright. Hopfully I don't get a dick.
I think it would interesting with a tok'ra. Being able to see the experiences and knowledge gained from a long life. The health benefits are also a plus. The chance of a bad experience can't be ignored like what ended up happening to Jack. The goa'uld would be a big no. Even the baby goa'uld the Jaffa carry are just a parasite waiting to take over completely.
Imteresting question! I'd possibly consider a Tok'Ra. Imagine the knowledge, the memories and experiences of several lifetimes! Though it comes with it's dangers as well, like acting double agent and being a hunted man for the rest of my life...