Your major has absolutely nothing to do with your college at UCSD. Changing your major has no impact on switching colleges or impacting what college you get thrown in. In general Warren and Sixth are geared more towards engineers though, seeing as many GEs will coincide with your major.
I'm in Sixth College right now, and the work load really isn't that bad at all. The only core GE that's gonna suck is CAT [Culture, Art, and Technolody] and even it's not that bad by the third quarter (I'm in CAT3D and our topic is the impact and relationship video games have on modern culture) Unfortunately if you don't get into one of the Sixth Apartments, you should be prepared to have the worst housing on campus (strictly my opinion.) It's nicknamed "camp-snoopy" for a reason, the dorms pretty much feel like 6th grade summer camp or something, which a lot of people like. Not for me though. On the bright side, the Sixth Apartments are awesome: 2 stories, 4 singles, 2 bathrooms, living room, kitchen. Not too shabby. On top of that 1st years can apply for the apartments. Word.
As far as engineering goes UCSD is pretty much top notch, specifically BENG which happens to be my major (ranked #2 in the nation behind John Hopkins,) but EE is really solid here as well. Of course UCLA is UCLA, so many people prefer it simply because of their solid academic name and outstanding sports programs. In many majors (probably most) I'd pick UCLA, but personally I feel like UCSD has the edge on them in engineering.
Coming from someone who got into both colleges, I honestly went to UCSD simply because I didn't make the cut for UCLA's track & cross country team (4:19 mile doesn't cut it at UCLA, haha) Welcome week was a blast, but after that (not gonna lie) I felt like I made the wrong decision for the first few weeks, speaking purely about the social life. The social scene at UCSD is pretty dull. Finally I decided to do something about it and go out looking for people in clubs with common interests and what-not, turns out UCSD has sociable after all, but you are going to have to make the effort and look for them. Academically speaking, I haven't had any doubts about UCSD.
Don't let what your friend says about Sixth GE's discourage you in your decision between UCSD and UCLA though, Revelle and ERC are waaaay worse than Sixth. Marshall and Warren are roughly even with Sixth (Marshall being a bit more work, Warren being a bit less.) Muir is really the only college that has it significantly easier than Sixth. Ultimately it depends on what your personal values are. UCLA has a lot to offer that UCSD simply can't: Division 1 NCAA sports that consistently place well, an actual Frat row, and real school spirit. UCLA also excels in many majors that UCSD falls short in, specifically business (which UCSD is getting better at.) Like I said earlier though, UCSD has a first rate engineering department, not to mention you're less than a mile from Blacks Beach which has the best surf in California, bar none. Good luck on your decisions.
