Maggie MMG versus Ls3/5a

Chances are good LS3/5a's would stomp MMGs.

MMG's are terribly inefficient, the very LAST thing they are is dynamic !
I never heard the Tekton, but every review says they are dynamic.

MMGs are very good for microdynamics/transients but not for macrodynamics/"slam", ie dynamics you can feel as well as hear.

I would expect significant sound differences between Magnepan in general and Ls3/5a or any similar British monitor.

You might consider more high efficiency horn designs for that. Might not have to cost a lot or be too big if lowest octaves are not a concern, similar to mmg.

IMO, MMGs provide great value at $600/pr., but they do have limitations in dynamics and deep bass. Then again, I'm not familiar with any $600/pr speakers that don't have limitations. Certainly the LS35a shares those very same issues with the MMG. Presumably, the OP uses bass extenders in part to address those issues, so.....

I took a similar approach and use MMGs with subwoofers. Freed of heavy lifting below 80hz, they sound really, really good (to my ear, anyway) - better than any other speaker system that I've heard at the price point, and by a pretty wide margin (again IMO). There are a lot of good speakers at +/- $2k, but a pair of MMGs with a pair of good $1400 subs is that rare option that will also provide true deep bass. Dynamics are very good, tho ultimate SPLs remain limited. Timbre is excellent and octave to octave balance is satisfying, even if the high end may strike some as a touch dry. I find that imaging is also convincing, provided you like the way planar speakers image. (Not everyone does.)

OTOH, to make such a system sing you need to properly integrate the subs. I cross actively and the appropriate electronics will add to the total system cost. There are a lot of ways to skin a cat in this price range, but I do like the MMG+ sub+active electronics approach. Just one more data point for the OP to consider.

To different speakers its not VS its what you like!!