Great question. I would suggest you strive to use the same version your customer is using so you can manage expectations. Interesting question though. I'm not aware of a Beta version, other than PlanIQ which is now been released. What features are in the Beta version that aren't in the released version? That should help answer your question more specifically. If the features are not necessary for your customer then you may want to use the same one as the customer. Hope this helps.
Ah, okay. That's the same version as everyone else's. However, because it's a 90 day trial, you'll want to build customer applications in their tenant. Use the 90-day trial to earn your certifications.