MP5-K, easier to control on full auto, heavier than the Glock so it'll take more of the recoil. Plus two hands holding the same thing (grip of Glock) will always be less stable than one hand holding onto each end (pistol grip and foregrip on the HK).
Not knocking the Glock though, and I guess if it's in a space as small as some of the homes in Italy that I went into then all you need is a little super-soaker like that. They're both bullet hoses but I'd probably go with the MP5-K if it were me.