Always a dilemma

Even with 3GB of RAM, my Macbook still seems to be able to use up all of it. I have a non-Santa Rosa Macbook so I can't go past 3.3GB. A refurbished 2.2 Blackbook is $1299, it also has better graphics and can support 4GB of RAM but its still missing some features in which only a Macbook Pro has...
What I love about Macbooks:
- user replaceable RAM, HDD and battery
- small form factor
What I love about Macbook Pros:
- 15" LED screen -> higher resolution
- backlit keyboard