I would NOT want to go into a wedding with full frame only. I did that for like 10 years (film) before getting my first crop cam, a 20D. Putting lenses on my 20D was an eye opening experience for me. I felt like I had suddenly increased my gear bag without actually buying any more lenses. Since then, I would never want to shoot full frame only.
For weddings and portraits, I have found crop to give me more options. I get a lot more "reach" out of my 70-200, and EF-S covers me exceptionally well at the wide and ultra-wide end. To get a head and shoulders closeup of a speech on FF at 200mm, you still gotta be pretty darn close. I love being far away so I don't give people a panoramic view of my ass. The lenses are lighter, I can carry less stuff (i.e. I stopped carrying around a 135 f/2 because my 85 1.8 on a crop gives me the same reach). The DOF difference I could care less about, I get plenty thin DOF with crop at 1.2. In this day and age, image quality is so good on crops that the difference is negligible IMO for wedding work.
So for that reason, if I had to choose between FF only or crop only, it would be crop only. But Crop and FF together is ideal.
Now, for commercial, my options are larger with FF, so I shoot all commercial with FF. It all depends on your scenarios. But weddings and portraits... crop MUST be in my bag.