None is really better at maintaining gains after the cycle. That is a matter of how you eat, behave, train and run your PCT. Something you will probably see is additional “weight gain” from the Deca that you won’t see with the Boldenone. That “weight” gain however will be additional water, especially if you don’t manage your AI during your cycle. Boldenone will keep you tighter, drier and looking better than Deca, but you will get much more out of Deca from a size gains and strength perspective. You COULD get similar gains from Boldenone, but the amount you would take would be pretty cost prohibitive. Something around 1,000mg per week of Boldenone… not worth it.
As I said, I've never ran it alone so it'd be hard to say. What I do know is, that with no more than 300-400mg of either test, deca, or EQ, the combination of all three definitely works. I trained for a year and a half naturally and put on about 25-30lbs of muscle, give or take. Since I started using steroids 3 years ago, with the test/deca/EQ cycle making up the main compounds of choice in most of the cycles in that time, I've put on another 40-50lbs of muscle, with my training being totally inconsistent throughout most of 2016 and cruising through a lot of that year. People might say 300-400mg of any compound is too low, and if it's run in its own I'd agree - but if you're on something like 400mg test, 300mg deca and 400mg EQ just as a weird example, that's over a gram of gear, which in total is a lot unless you're very experienced.