Are you going to run STFs? You have some flexibility in both vessels.
The Odyssey Class starships are tanks! But do you want to be a tank towards ENG/SCI/TAC?
I bought the 3 pack and usually run the
Tac Odyssey myself. Lt. Cmd uni and Ens Uni make it... fun. But you can't turn this ship... that's the downside. It's the largest cruiser Starfleet has ever built. But you can hull tank... and with such a large crew, you need to repair the ship as long as you can keep the crew alive. Or just get the
Ops Odyssey for saucer separation.
The Vesta Class starships are high end sci ships! Same question: do you want a sci oriented ENG/SCI/TAC?
I only bought the
Tac Vesta this time since I also bought the
Steamrunner Class pack at the same time. Vestas can mount cannons but only 3 fore/ 3 aft weapons. It has a hanger bay... so that's good for crowd control with Danube Class runabouts or glass DPS fighters like the Peregrine Class fighters. Lt. Cmd and Ens uni slots are there for your builds.
As engineers, you can tank in both ships. Remember... T5 escorts are also fun as an engineer. My Joined Trill flew the Steamrunner Class as it's very tanky and is a Fleet vessel minus the name (10 consoles, same hull as Heavy Destroyers, has 2 Lt. Eng BOFF slots).