Some people tell me that it is better to lower my comp. ratio and some say it is better to raise it... So what is the difference between the two and what do each of them do performance wise?
8.8-1 Vs. 10.5-1

Each point of compression is worth approx 3-4%. A lot of it depends on the setup you are going for. If you want to be turbo with a lot of boost then most prefer lower compression. If you want to be NA or N20 then you probably want higher. Such as me for example I run 10.5:1 pistons with the head milled and block decked, so that I have some pretty high compression for NA. Another big factor is fuel tuning. If you are looking higher compression turbo, then you will need to have more control over fuel and timing.