£1.4k to spend on a mac

[bimmerboii]

Originaly the money was supposed to go to a top spec imac through HE.
But when apple released the updated mb and mbp, I was able to cancel my order and wait for the newer imac. Now the mbp looks so tempting, but paying a huge premium for a notebook dont do it justice for me. With this money i can only get the 15".. and i have been using/used to 22" all my life (im a pc owner). Also having a laptop for home use doesnt seem right to me so i decided to go for this instead:
Buy the 20" imac for home use and a macbook when i travel. Ill get 2 machines for the price of a single mbp.. Which is the better deal?

 

[bimmerboii]

i do not do any video editing or photoshop.. just email, web surf and office apps.. however, I do sometimes use autocad and sketchup. though im thinking the macbook wont be able to handle this?

edit: the imac wil be my main computer (obviously) so ill be doing my work here. The only "heavy" work I can think of is autocad and sketchup. I remember the university computers I use before ran autocad and sketchup fine with just having onboard graphics.

the macbook will be for my travels since my father and I do business trips a lot. I may need to run autocad and sketchup occasionally on the macbook as well (for viewing and a quick edit maybe)