If it was a "chore" and "work", then you weren't experienced enough.
This might be true for me, but certainly not for other members of my group who have DMed games 10 years longer then me. And they still prefer 4E.
So I consider this








.
4E is easier to DM for, and even an inexperienced DM can get good results, thanks to the "hand-holding". But if you're already an experienced DM, it's still easier to get good results. I just don't see how 3E can give me better results. I just see where DMing because more difficult - I have mastered D&D (or rather Arcana Evolved) in the 10+ regions of D&D, and I've seen others master it at that level. It was a lot of work.
When players were to go back to a new session, they usually refamiliarized themselves with their PCs in maybe an hour or so (some take less, if they don't do too complicated stuff with the PCs). But the DM has to do this for dozens of monsters, and each time he has to look up special abilities, tactical options, spells and so on.
And as a DM, I still missed options that could have made encounters more interesting (or just make the monster worth its CR)
In 4E, I read up the encounters and the basic plot points (taking no longer then 2h), and are ready to go. Heck, I am not sure I really need to read up the encounters (in fact, in our last session; I didn't look too close at most of them, mostly focusing on the adventuring details - what kind of information is hidden where, any special hazards I need to be aware of, and so on). And trust me, the encounters were all interesting, challenging and never boring. And the whole XP budget system and monster levels also made things a lot easier - I even reshuffled the encounter groups a little after the PCs retreated (remanning the entrance defense and stuff like that). (Just as I did in 3E, but even faster.)
I don't think it has anything to do with experience that I don't like to study monster stat-block and reference the PHB spell descriptions to understand what a monster does (possibly re-reading stuff during a running encounter). It's just the kind of work I don't like to do, that bogs down my preparation and my game. Others may like this kind of "explorative" DMing - I am not one of them.