Luna is a relatively new reel...
The 253 has 11lbs of drag compare to the calcutta 300 which has 15lbs of drag.
The magnetic adjust side plate might be a problem in salt water, or dirt or sand will have a chance to get in... That has to wait and see...
Differences with magnetic system compare to SVS system in general:
Distance - SVS wins
Ultra light weight lure - Magnetic wins
And one last thing, you cannot turn off the magnetic system. Test has been done and eventhough you turn the magnetic to zero, it will still has mininual magnetic force so there is no true free spool.
I am not sure about the all metal line guide... it worrys me...
And lastly, using a reel for 10 times can't tell if it is a good reel. I have a Shimano Chronarch A 100 since 1997 and been using it till now from bass, catfish, dogfish, rockcod, lings, salmon, and 4footer stugeon, etc. I put that reel to hell and until now, I only have a little bit of corrosion in the bearing...
Don't get me wrong, I am a big Daiwa fan. I use Daiwa Saltiga for my salt water setup for small tuna up to 40-50lbs... It is a light weight ultra strong reel.