Mauritius and the Seychelles are identical on many aspects...it's just that Mauritius are much more build-up and more populous. I have been to Seychelles for holidays so I won't be able to talk about their administrative and business environment.
Mauritius:
As an expat, to work as a dentist, you will have to be employed by a medical or dental institution as a professional if you demonstrate qualifications and a competency level not available on the island. Or you can set up your own practice as an investor or self-employed. In both cases, you will need an Occupational Permit with conditions attached.
Salaries vary greatly depending on where you are working and level of services provided.
Cost of living: Rent + Utilities + Travel + Upkeep + insurance + randoms will cost you around min. MUR 45,000 (approx. $1,500) monthly. However, this also depends on your way of life...you can keep it close to a reasonable margin or it can shoot up as well. E.g: Living on local delicacies or eating out in fancy restaurants everyday will cause a marked difference on your credit card statement.
Country and local women: Mauritius is a highly conservative, family-oriented and socially complex society but this also depends on the ethnic/religious group...some are more conservative than others. The dating scene are somewhat related to this so don't expect anything like in Europe or elsewhere.
International crowd: Definitely the Northern and Western parts of the island...and other coastal and resorts areas. However, quite some expats do live in the central regions and towns for working and business convenience.
Locals: Again related to what I said above on the Mauritian society...however most locals are friendly and easy-going and don't really hold grudges against expats. Though it might be hard in the beginning, once you build yourself a circle through your work, things will work out by themselves.
Port Louis: PL is the business, commercial, administrative and political heart of Mauritius. It's crowded, busy, noisy, polluted and hectic like any other city. However, at dusk, it slows down and practically dead at night except in some quarters.
Conclusion: Mauritius is a great and popular place in general owing to the large number of foreigners wishing to settle here but like anywhere else, it has its own character, culture, way of life and traditions and up to you to paddle your way though. That's why, it is always recommended to come as a tourist first for some time to get a first-hand experience and then decide whether you are willing to take the plunge!