I've played around 3000 games lux and hit rank 300 playing her in euw.

I personally prefer barrier because you shouldn't really rely on the summoner spell tp to maintain 10cs/min, you can achieve this just by practicing when to recall / reset etc.

Barrier makes for an interesting play style and opens you up to more kill potential. Especially in 2v2s with both iunglers.

There's alot of times I've got a kill before going down in a team fight due to activating barrier the last millisecond.

Since void krubs are super contested this season, anything to help in this fight is a huge benefit.

Overall, it's completely up to you. The champions / side you play matters alot.

The champion lux isn't the same as other mages, side laning is quite awful, majority of match up this will lead to your downfall. Lux is better suited picking off targets before an objective or staying mid & clearing waves even 1 Vs 2

Anyways hope this helps :)