For me there was no specific reason. But once i got to Mauritius and met the american couple that told us Mauritius was so much better than Seychelles maybe that can be a reason for you.
We did Seychelles in January and can tell you that it is amazing. Hopefully will get to a trip report, but we did Dubai, Abu Dhabi, Praslin, La Digue, Mahe, Cape Town, and then a safari.
Pros for Seychelles:
- One island had nothing but bikes to get around and it was so much fun.
- Very easy to rent a car and find a private pristine beach that is picturesque and have it all to yourself.
- Has a few beaches that are typically always ranked top ten in the world.
- Flights to/from UAE and JNB make it just as easy as MRU to get to. (I think I paid $330 one way to get to CPT from SEZ)
Negatives:
- The accommodations are either very high end, somewhat over priced Airbnbs, self catering apartments, or budget hotels.
- Not sure how Mauritius is, but like most islands outside of southeast Asia the customer service isn't the best.
- Going out to eat can be pricey.
I would say that a majority of people who have been to both usually state a preference of Seychelles over Mauritius, but we've yet to go to Mauritius. I don't think I would go out of my way to go back to the Seychelles because it's not easy to get to, but we were very happy with our choice. Mauritius looks fantastic as well. I will say that we did not see many Americans in the Seychelles. Mostly French and Italian. There is also a lot more island hopping which we enjoy. Even in peak season (Christmas and New Years) the most popular beaches weren't the crowded and it was extremely easy to find nice secluded spots where you might not see another person all day. I think Mauritius is going to have better beaches at the high end resorts, whereas the Seychelles' best beaches were typically not next to large resorts with the exception of Mahe.