Dell Inspiron 15 v. 1525

I'm looking at the Inspiron 15, but avoiding the Inspiron 1525 because the fan was unacceptably loud and intrusive. My question is, though, does the Inspiron 15 have the same intrusive fan? What is the basic difference between both models?

Also, what is the best processor nowadays on the DELL models. Is it:

Intel® Pentium® Dual-Core Processor T4200
Intel® Core™ 2 Duo Processor T6400
Intel® Core™ 2 Duo Processor P8400

One thing I want to avoid is the screen freezing up when I have a few programs or windows running at once. Do I look for a higher RAM, to avoid this? What sort of RAM? I really have very little running but MS WORD, ITunes, and, perhaps six of seven tabs open in the single IE window- but I don't want the entire computer to freeze because I want to open my photos folder. Any advice would be great.

Thanks in anticipation.