You might be mixing up difficulty and profitability. Those are not the same thing. Difficulty is usually not something you should worry about. Most profitable coins to mine with GPUs all have very high difficulties. And most of the coins with very low diff aren't worth mining at all, no matter what hardware you've got.

There's no right or wrong answer to this, it's the same as selecting between two different cars. One is better at some things, and the other is better at the others.