Great question! Microneedling and microdermabrasion can be combined and done in the same visit for maximum results! By doing microdermabrasion prior to numbing the skin you can get better absorption of the numbing agent and achieve the best result needling on freshly exfoliated skin.
However, if you are only able to do one treatment I would advise the microneedling. Microneedling encourages the skin to make new collagen that will help to even out your texture issues while erasing hyperpigmentation.
Microdermabrasion is a great treatment for exfoliation and circulation but when dealing with issues of scarring and hyperpigmentation. I also recommend using a retin-A and Hydroquinone in your home care regimen to create the healthiest environment for cellular regeneration.