IMO, for the price, I would get them both. Both offer the almost the same performance but the BlackViper USP Tactical Gas comes with a suppressor while you cannot add one to the LS M9 gas blowback pistol. The LS M9 is more realistic and it looks and functions like a true 1911 would.
"There is no hunting like the hunting of man, and those who have hunted armed men long enough and liked it, never care for anything else thereafter." - Hemingway
The greatest ignorance is to reject something you know nothing about.