memory or processor speed?

Personally the difference in screen sizes is enough to make a difference (15 vs. 12), especially since you USE Photoshop. I don't think I've met anyone who wouldn't mind a larger working area (this girl went from an old dying 14" CRT to a Sony LCD 17"...needless to say, she continues to Photoshop )

The cpu diff between 1330 and 1250 is not significant when you consider how much more RAM you will have (compared to your current) and 3" more visual real estate.

I would definitely take the 15" with more RAM.

 

Also take into consideration the graphics card. The 12" comes with 64MB and the 15" can get up to 128MB. If that's not a problem, I'd go with the 12" since you have an external display.

JOD8FY

 

for on the road editing id prefer a 15 over a 12, but if u have a screen and arent moving around too much stick witht he 12

 

More ram will only make a difference if you actually require it i.e. if your system isn't paging out to disk that often then extra ram is not going to speed anything up... the processor speed will make more difference. Obviously its hard to test this unless you have the machine there to test it on

Of course if your images are super large and cant fit into memory then the extra ram might be useful (and noticeable). Just how big are these images that you work on?

FWIW I would get the updated model on the assumption that many of the previous issues have been sorted out.