Obviously if he said he wants an Mp5 or an Ak he wants an MP5 or an ak... Bassick man stick to what he's askin please
On Topic: If I had my choice I'd get the Mp5 simply because its got a metal body, will last you longer and is made by a good company. Another alternative is the new 2006 Version ICS Mp5's which IMO arnt as good as the new CA Mp5's (Make sure the CA your looking at is B&T if not, get the ics) The B&T version comes with a new hop up system that is more reliable then the older versions and stays put. It also has Trades which may be a big thing for you (I know they are for me) which enhances the realism...
If you want an AK dont get a UTG, get either the new CYMA Ak's (which I think are better then the stock TM, but thats an oppinion) or buy a TM one. Both will last quite some time and come with their own slew of accessories to add on to.
Now if you like Bassick's idea (which i agree with) also consider the new 2006 ICS M4/M16 series. It comes with a split gearbox which means you can go from switching from a CQB FPS set up to a Woodland(hah, woodland) FPS Set up in a matter of seconds by only taking down one reciever pin. The foward assist also decompresses the spring which gives longevity to your spring and helps it retain its power during storage
Occasionaly on jams it will help reset the gearbox so you can clear jams easier. It also now comes with Metal bushings, reinforced gears, thicker wires for higher voltage and the same one peice hop up which will stay in place better then the CA. However it is not w/out its disadvantages. I've run approx 50,000 rounds through my gun and the Switch assembly is starting to go bad on my gun and the Hop Up probably needs replacing but this is common to ALL M4/M16's made by all companies
If you wanted my honest oppinion drop both the ICS and the CA and grab the WGC Shop Custom M16's which are G&P Externals with reworked internals for better reliability.