Who to upgrade?

I wanna bring a champ to 60 i was sure i was gonna do a argonites like slither or tidemaster since i just got pallas to 60 but I've been messing with other champs now I'm thinking shamrock or samar. I was surprised with samar survivability he was the last one standing with auto equipped gear and lvl 50 so now i have 4 . Which one out of the 4 should i upgrade