I tried an EF 28/2.8 (300D). I was disappointed due to chromatic aberration and corner softness at f2.8 - I had expected it to be better than my f4 zoom at ~f4, but it was worse.
Is this typical? I suppose so. You could try one.
I'm not clear about what you want to achieve. Church lighting varies a lot, f2.8 does not give much depth of field with 28/30mm for "architecture" - it sounds like you are not expecting to be able to use a tripod or flash.
In that case, for handheld photography indoors a lens with IS, stopped down a bit, might be worth considering (not that there is a big choice around 28mm, and they are more expensive).
A friend has the EF 24/f2.8 and it seems a bit better than the 28 ( but I did not do a very careful comparison).
At f2.8 focus unsharpness is likely to be the problem with 3D subjects.