For your budget you should look for an i5 laptop.
I use Apple at work and they are absolute rip offYou can get double if not triple the spec for about 1/2 the price if you stick to intel chips - AMD are even cheaper and if all you are doing is word processing or watching vids online that might be a good option.
Of all the laptops I have owned over the years my favorite are Acer - my current laptop is an e1-571 i5-3230m 2.6ghz with turbo boost 3.2ghz, 4gig ram - I use it for after effects and editing no problems. I got mine for a steal - £349. ( best way to search for a good laptop is to go by the intel chip and try and find the best laptop in your price range with the highest spec.
My last i3 acer lasted for years and was literally on 24hrs a day.
Probably a lay question so apologies, but re RAM/CPU. My current machine has 4gb of RAM, and most of the machines in my price range seem to have this too (my current machine is 5 years old). Does that matter or will a better processor provide enough of a boost in performance? My current CPU is Pentium Dual-Core CPU T4300 @ 2.10GHz (whatever that really means)