Buried microstrip vs Top Layer
As mentioned in comments, reducing vias in the signal path will likely improve performance.

If you have the space, there are advantages to a wider microstrip line:


Can handle higher power (not likely an issue for Bluetooth)
Better impedance control due to etching errors being smaller relative to the trace width


The trade-off is of course the board area used. You need to consider not just the trace width, but also the desire for 3-5 trace widths of clearance around the trace to maintain controlled impedance.

If there are no other issues, a top layer microstrip is probably better than a buried one. If the space required is too much, then consider using a thinner dielectric layer to allow you to reduce the trace width, rather than burying the microstrip.

One scenario where the buried microstrip (or stripline) would be better is if the board will be used where there are conductive materials (like the lid of the enclosure) close enough to the board to disturb the impedance of a top-layer microstrip.