i think i want to get a cyma platinum mp5, mainly because
>cheap and no hassle due to AEG
>metal construction
>extendable stock (even if i like folding stocks aesthetically more, i must admit they suck to use)
>lots of rail systems, can detach handguard and attach optics easily, etc. etc. (very important)
i haven't decided if i want to get the mp5 or the mp5k though

short
>can be both a primary and maybe a sidearm with a really good chest/hip attachment system
>can be made longer with a suppressor if needed
>could do some silly shit with it because it's so small, fire it one handed and stuff
long
>probably a bit more ergonomic for actual shooting
>25% more length but 100% longer inner barrel
>looks a bit cooler
>not *too* much heavier or longer than the mp5k, could probably still run it as a comically large MED secondary still
>can actually get it for a bit cheaper

i was leaning towards the short version but i see some benefit to the long one too