for just creating a 3d model to manipulate then both systems are quite capable of producing what you want.
for future integration it will be much much easier to upgrade the d500 to 800/900 than it will be to get better quality and more advanced software out of the maestro.
Maestro make their own scanner and their own full featured Scanning Software, Advanced Ortho Software and just about to be released a Decent Dental CAD for crowns Bridges etc.
Not many companies do all that... only 2 that I know of and maestro is one of them.
I dont believe the dental CAD is advanced as say exocad or 3Shape but it does the meat and potatoes stuff just fine.
The MDS 400 Scanner from Maestro does a great job, it's a striped light colour scanner, and while others are using "blue" Maestro is capable of ANY colour you wish to tune it to, "blue" included. Its also easily programable, ...programable... ??? yes with a few easy commands you can get the scanner to do scan in any angle/pattern, shape you like.
It also scans impressions better and faster and more predictable than any scanner i have seen.
One of its features is a virtual 360 degree scan feature which is very cool, and the process is very, very clever.
So it has lots of features, its also about
HALF the price of a 3Shape D900 Scanner.
What is best? Who knows.. each company will tell you theirs is best, the fairest way would be an independent study, i would love to see that.
Both the D900 and the MDS400 are very good scanners..i suggest try both...at least get scans from both and compare.
What I do know , if you are interested in doing some scanning/digital models with Ortho software, then the Maestro is a very affordable solution, that will give you an viable upgrade path just incase if you want to get into C and B and implant work.
BTW The scans from the Maestro can also be imported to 3 Shape with not too much effort and the scanner works directly with exocad as well.
If anyone would like some scans to look at , don't hesitate to contact me.