I have an EOS 3 (and an EOS 5, an EOS 1 and an EOS 1n).
Looking at the differences between these 4 cameras:
The EOS 5 is more plasticy and flimsy, and I find the built-in flash terrible, especially since you cannot switch it off in the automatic modes. Fortunately I slammed it down so often that one happy day the flash gave up and never reappeared. Much better!
The EOS 1 and 1n are more rugged and more compact, and the 1n is also water-resistant. A bit heavier though than the EOS 3.
The EOS 3 eye-controlled focus is brilliant but doesn't work well with glasses. So in my case it's pretty useless.
Bottom-line: if you don't wear glasses, the EOS 3 is superb due to the very sophisticated eye-controlled focus. If you wear glasses or you need a very rugged and/or water-resistant camera you're better off with an EOS 1 / 1n / 1v.
The "BC error" can also occur due to other reasons than dirty battery contacts. I sometimes get it when using old manual lenses under low-light conditions. Power off - power on will fix it but it is annoying.