Question 1 how much space do you have?
Metroplex is MASSIVE. if you are limited for space he might just not be practical.
I have my Metroplex on display on a shelf in robot mode as the other modes just don't fit anywhere in our apartment.

I question if the shuttle geometry will suit the size/shape of transformers legends, the platforms and ramps that suit the star wars figures might be too narrow for the little transformers. This is a guess from the pictures and video in your link. while the shuttle is smaller overall, it doesn't really have a mode that doesn't take up a lot of real estate, at least with Metroplex his robot mode has a comparatively small footprint even it is 2 feet tall at the same time.

the transport mode of Metroplex is good for displaying legions in vehicle modes, especially the aircraft. you can fit a lot on there.

Personally as much as I really like star wars, it's not transformers and therefore my advice is Metroplex, but the above needs to be considered. I have Fortress Maximus as well, I got it out of the box, changed its modes a couple times and then put it back in the box in the cupboard because there was no-where to display it without it getting in the way. this might be the biggest issue with city formers. Of course if they came out with a Titan Trypticon I would buy it in a heartbeat.