im in a similar situation, stuck between downpour or HD, but i have played several silent hills (1,2,4, origins, homecoming). if you want a "newer" experience but dont want to spend the money, im sure you can buy homecoming for $20 or less now. its been several years since i played it, but i really enjoyed it at the time.
I bought the HD collection, but i havent opened it bc I am still deciding whether to take it back and get downpour. i dusted off my ps2 to play the original SH2 to help weigh in on my decision, damn game still creeps me the hell out!