Whats the difference between entering on the base, final as you say, verses on the 45?
The 45 isn't part of the pattern. It's a recommended entry to the pattern.
I'm not a big fan of the 45, because, yes, it invites converging traffic, some of it descending, but at least that's expected out there wherever it is the 45 is supposed to begin.
Not so in the pattern.
Descending into the pattern (crosswind, downwind, base, final, upwind) is bad because the chances of you descending onto (or into the path of) an aircraft you can't see (who also can't see you) improve astronomically.
The Bonanza pilot I mentioned in the "Pattern Madness" thread did just that, and it cheesed me off because I doubt he saw me, even though I'd responded to his initial call- up (which gave an inaccurate position, BTW) by mentioning that I was halfway through the downwind leg. I didn't see him until I was about to turn base (came out of my high-wing blind spot)... he was diving onto the base leg with everything hanging out, from who knows what altitude.
He had not announced he'd be doing this, nor was I expecting him to be so close already, based on his initial callup. He appeared right in front of me, not so close that I had to maneuver away, but way closer than would be considered sensible without prior arrangement. Had I been going a little faster, or had been in the midst of my turn to base, eyeballing the runway, I would probably not be sitting here typing this. Quite a surprise, and not a pleasant one.
He probably thought it was pretty slick flying, but I think it was one of the dumbest pilot tricks I've ever seen.