I play with both so my 2 cents are:
If you play with less-lethal sometimes it hard especially if the sus has heavy amor and sometimes even the beanshotty doesn't even react to the sus, and being in 1 room with 4 sus on TSS while aresting there is a change that one of them get up and shoot you while aresting, so it takes a little patient, also aiming your nade with the launcher at the sus is sometimes a challenge.
If you play lethal, it is hard to shoot at times guess if you kill a suspect wrong you get penaltys, there are time that it is questionable too shoot or not and that might kill you at that time, offcourse it is a game with flaws guess sometimes you shoot in your right and game still counts as unauthorised, that one second if doubt of shooting makes all the difference.
So both sides can be hard or easy.
Both the hardness or eassyness all depends on the team you have with you
.