Where would you put your Bond Equipment?

I'll make it short and sweet, with the Well Deserved Reward I'll have enough bonds for two pieces of equipment. I hate playing ranked and don't partake in any other events really, just casual pub gaming. I have the 121b and the M60 and can't be bothered to save for what tank might appear in the bond shop later on.

I have every single tier X (Apart from an arty and the Type 5 which I'll buy sometime in the future) and would like to take one of them to the next level with bond equipment. I have a few other tanks with a bond setup, but would like to hear what y'all would suggest?

Obviously I'd like to put it on a tank on which it'll actually make a difference, if that makes any sense. Making a good tank a little better is less tempting than taking a tank I rarely play and revolutionize it with stacked equipment.

Thoughts?