Second one is better, but at 500 pts a flier is a little expensive for what it does. You have to wait for it to come on, it takes a large chunk of pts out, and it can be useless at lower level games since blobs are common in the lower level games. Not to mention people may hate you.
Maybe take a primaris psyker, put him in with some vets, get rid of one melta, and then buy a leman russ tank? AV14 will make people hate you too, but at least they aren't skyfiring at it hah.
The meltas on the vets are alright, but the anti terminator is good to have at least.
I would put 3 meltas in one chimera then the primaris with the vets in the other chimera so you don't mix roles.
Dear Lord the IG has tons of Dakka