So if that's correct - I conclude that for people like me, who are mining with high intensity and who are therefore taking a higher risk of getting rejects, pool-mining a coin with a higher difficulty (more time until a block is found) are better of, cause it results in fewer rejects.
Correct?
No it is irrelevant. Difficulty doesn't affect the time between block changes.
When setting a worker's diff in a pool to a low valule, let's say 32, the number of accepted shares is way higer then with a worker diff of 1024. So I assume you get not only paid for the number of accepted shares but also the size of the batch. Otherwise all people would be mining at diff 32, right?
Share difficulty, min pool share difficulty, and block difficulty all have nothing to do with intensity (batch size).
Intensity defines how long the card will run (in hashes) before it ends the batch, drops off results, and picks up new instructions.
You are right (but using wrong words) in that pools pay based on the total difficulty of the shares accepted not the raw number of shares. A miner with lower difficulty will produce more shares but each share is worth less and a miner running at higher difficulty will produce less shares but each share is worth more. As an analogy someone depositing one $100 bill into the register gets no more credit than someone else depositing one hundred $1 bills in the register. This has nothing to do with intensity though.