Well, lets look at Jug stats in general. All jugs are pretty much a slightly weaker version of their wild counter parts. (new jugs closed the gap alot but its still aparent.) Now if u figure in the mob stats between the top two.
Ruszor has: Crazy high atk and HP ratings (more than a sheep.) but basicly no outstanding draw backs other than its large size and we all SE can /bite size mobs now.
Slime has: Mega low HP and mega damage resistance.
So if u add the mobs + jug stats together you'll end up with
Ruszor having High attack and HP and some vicious TP moves even with out the added effect.
Slime having: Very low HP and most likely Lower defence. Even if they keep the physical resistances
almost every NM in the game has Magic or a Magic ability or an En-spell or a Spike effect that will Tear the
slime apart.
My Vote: Ruszor
out of the runner ups I'd take Hippo as we need a new THF jug