True but it's just arithmetic. Never had much of an issue with it.
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Great. I'm not trying to score edition points and I've no doubt 5e will be easier to DM, though I enjoy the effort 3e takes; it's part of why I play D&D in the first place. I'm just saying certain aspects of 3e are more to my taste and - here's a thing - I actually have all this 3e stuff already, along with a group of friends who enjoy it with me once a month. So I'm looking forward to buying, reading and running 5e games but I'm unlikely to abandon 3e because of it.
I like driving modern, well-equipped cars. I also enjoy belting along country roads in a classic sports car that has no ABS, power steering, lane-departure warning indicators or parking proximity sensors.
Actually, my point about flatter math isn't that it's easier to calculate to-hit/defenses, that's just arithmetic, just as you say. My point was that you can use a wider range of monsters. In 3e, the to-hit/defenses scale pretty steeply, so you want to avoid using low level monsters because they just can't hit the PC's - or vice versa.
Regarding not abandoning a game that runs well? I really see your point here. I am currently running a really cool low-level 4e campaign (level 1-8, currently at 3), and I am not abandoning it even if I like 5e better. I have started a paralell 5e campaign though with the starter set, mostly to see how 5e is actually like, not just on paper. So far, I really like it and am confident that it will run really well up until level 10-ish.
I think I would need to run a high level campaign to see if the changes they made to 5e high level play actually are improvements, and if they are good enough to make high level play enjoyable. For me, it's not so important, I have always preferred level 3-7 anyway due to the different campaign style high level play often entails.