Why is this not recommended yet.. no idea but here why..
Both are works of the Great Tomino, and both are very light hearted really. The atmosphere of both are similar and both have this sort of goofy nature with the MCs. Also the mecha designs are similar as well, the character design is also the same.
I would say if you're looking for more of "Happy Tomino" then try these out. Overman King Gainer has hardly any body count, but G-Reco does a little, and really G-Reco is a bit more darker,and somewhat serious then Overman King Gainer. Try them out, you won't be disappointed.