Brett Lawrie needs to learn to play his position under difficult conditions, and Las Vegas is that.  He needs to learn to play with huge distractions, and Las Vegas is that.  Plus, because you have $150-ish millions to spend at some time, doesn't mean you shouldn't be fiscally responsible with items like service time and such, now.

I voted No, Needs more minor league development. Let the scouts evaluate how he does against AAA veterans that throw a lot of off speed stuff. Eventually he will have to face elite ML pitchers. AA says that he wants to avoid trips back to the minors for prospects.
Whenever we are ready to compete, elite prospects have to be handled in a way that does the least harm to the competitiveness of the ML team. In the past K Gruber, P Hentgen & M Timlin were introduced to the Majors and somehow we still competed IMO.

I think he's close, but no harm in sending him down for at least two or three months, both for his further development and for service time reasons.

Lawrie, despite the laudatory scouting reports and spring training bulletins, has given little indication that he is ready to hit in the Majors.  Not only does he need more time in the minors, he needs to prove himself ready.  It's more than a question of whether he would benefit from more time in the Minors- it's that he still must show in the minors the capacity to produce at a high enough level.  Everyone assumes he will, but he has not as yet.