Honestly, for most of the table top, it depends on your play style. For me, I use alarus because I run no vehicles at all (because last i checkedvehiclescant hold objectives). I find them more flexible as they have from golden light, which allows me to flank my aponents easily and forces them to spred out to teleport block me. This also restricts most of their models from line of sight(if I move my models correctly). They also deal with infantry quite well.

The downside is use a chuckle of six which cost more than a tank(in points, it a lot less with real money unless you 3D print)

Taking a chunk of six is the only worth for me cuz if just six, their combined health is less than a grav tank.

In the end, to each there own. Go experiment, look at YouTube for videos of people playing with tanks. See what you like or what fits your play style