Should i buy the 500GB hdd for the price or 120GB ssd for the performance? Cus I dont think 120gb will last me for long.
A 120gb SSD will hold the OS and 6-10 games. It will make everything feel much quicker. It is one of the most effective performance upgrades you can make.
If your storage needs include large files, like video's, then you really do need a large hard drive. Larger drives, in the 1tb+ range are a bit faster because they are denser.
A SSD will help gaming with level loads, but not much else.
The amount of cache on a hard drive is a design tradeoff made by the engineers. Whatever size the drive has will be appropriate to the characteristics of the rest of the drive. Sometimes, I think the larger sizes are a marketing ploy, designed to justify a higher price for the drive. I would exclude cache size as a decision criteria.
Since hard drive prices are still historically high due to the Thailand floods, I suggest starting with a SSD and adding a hard drive
later when you need expansion.