Maxing out your character really has no point in Oblivion. Loot scaling stops at lvl 20-25 and enemies just become harder and harder to kill since they level up when you do. If you build your character wrong when leveling up that means they get stronger while you actually get weaker, and there′s no extras to look for in chests at lvl 40 compared to lvl 25ish.
On the plus side you get more health, magicka and fatigue, how much depends on how you level up. But this really is not a big plus if you ask me when facing that other stuff.
There are some quests that require that you are at a certain level, but those are all fairly low.
I′m lvl 50 and I don′t really feel stronger than when I was at lower levels and I really focused on combat and magic