Your question should be "but won't I learn more, get better instruction and more individual attention, be in a more positive learning environment and therefore have a better chance of success at a college than at UBC?"
Organic chem etc are not "easy" classes regardless of where you take them. You've still got to work your ass off to get a high grade (unless you're one of those people that is just comes naturally to, but then you wouldn't be in this situation).
I took Organic chem and other 1st and 2nd year science courses at Langara, and I think I can safely say I would not have done as well if I had taken them at UBC* (which is a sad reflection on the state of teaching at UBC and the whole "weeder" mentality as opposed to the emphasis on teaching and learning...). But these classes were by no means "easy" just because I took them at a so-called "Community College" for slackers and ******s who couldn't get into UBC*.
In theory, if you re-take them at UBC you should improve your grade since you have already been exposed to the material (and hopefully have improved your study habits, if that contributed at all to your less-than stellar marks). And for the same reasons you should do better if you re-take them at a college, but they won't simply be easier because they are at a college, but perhaps you will have a better experience because of some of the reasons I have mentioned above that make for a better learning environment.
I'm sure you realize that re-taking a class to get a better grade is going to take some work, but they way you have phrased that question is somewhat naive, so please don't take this as a personal attack. I know there are a lot of other students in the same boat and wondering if re-taking at a college is the way to go. Because I
actually took classes at a college I can offer first hand advice and help to dispel this myth that college is "easier". It's not easier per se, but probably somewhat less of a hell hole than UBC 1st/2nd year sci
Good luck.
* after a brief break after HS, I went to Langara, and eventually transferred into 3rd year at UBC; I had no desire to go to UBC after HS.