Ok so I'm just going to paste here what I wrote in another section of the forum, since it's pretty much the same post which I failed to see... :)
I'm an RRT and although I have not personally gone through nursing school, I do work closely with another therapist who has. Therefore, I'll just try to answer some of your questions as best as I can based on the experiences that he shared with me. First of all, it wouldn't be realistic for anyone here to tell you if the respiratory or the nursing school is harder because it's really individually dependent on your interest and your ability to learn certain concepts.
Before you decide which field you'd like to pursue, take a look at the curriculum of each program just to see what type of things you get to learn and ask yourself which to you are more interesting. I do think that most of the time the program will seem easier IF it's something that you like to learn because let's face it, if you're studying something that you're not really interested in, it will take a lot more effort for it to stick. If you're not doing too well in nursing school, try respiratory and you may like it so much you'll be soaking up the material like a sponge and do great. For some people, respiratory is too specialized and they'd rather learn a little bit about everything else instead of just focusing on breathing.
Now, the therapist that I told you about breezed through nursing school and graduated with a 4.0 GPA. According to him, nursing was a lot easier than the respiratory school but then again, he was already at an advantage having a strong critical care background and in respiratory, we're all in critical care unless you work in a sleep lab or do PFTs. So would nursing be a walk in the park for every therapist entering their program? Most likely not, they could probably do pretty well in some areas of nursing but others not. If you're not a therapist and are entering either program for the first time, well, then it'll just come down to your intellect and your desire to learn.
It's true that as a nurse you do have to know a little bit about a lot but you don't have to know everything about anything, nobody does. In my girlfriend's first nursing year which she just finished, she studied respiratory for 2 weeks, I studied respiratory for 2 years and I still don't know everything so I doubt she's ahead of me when it comes to breathing (she thinks she is though lol). As you work more, however, you will learn more and more about a lot, including respiratory if you get to work in the ICU but you will still never know everything. Some ICU nurses are very good when it comes to the respiratory stuff, but some don't have a clue and I often wonder who let them into the unit. But then again, some therapists don't have a clue about what they're doing and I also wonder who let them into the unit. It all comes down to the individual, not the two letters behind their name. There is a lot in nursing that I don't have a clue about but I promise you there are things in respiratory that I can talk about that'll make your head spin. Nursing isn't just wiping asses and respiratory isn't just giving treatments, you get out of it what you put into it. I'd tell you to stick with nursing just because there is more room for advancement, but always stay humble and do ask your RT colleague questions if you're interested in respiratory. I can't even begin to tell you how much I learned from my ICU RN friends by picking their brain and even though I specialize in lungs and partially in the heart only, everything is connected so it's nice to be able to get as big of a picture as you can. Whatever you pick, be a sponge and do the best you can. Let me know if you have any more questions that I can answer for you.
Forgot to say, as a respiratory therapist you are also on the front lines, more so than you think. It just depends on where you work, how much autonomy you get, how good you are and how bad the attending is. In one of the hospitals I work in if one of the patients' respiratory status deteriorates I can pretty much do whatever I want to fix him. If the doc orders something that I don't feel is beneficial or can be harmful (does happen) to the patient I can basically "recommend" something else and I will get it. In another hospital I work for, I basically do what the order says because most are really good docs and know very well what they're doing. Rarely will I have to say anything but sometimes I will if I feel I can contribute.