Since a Voigt peak considers mixing a gaussian with a Lorentzian, it is the normal result that you will obtain a better fit with it.
I recommend checking the literature on each specific case. XRD might work better with Lorentzian peaks. Raman with gaussian. You should use a Voigt peak only if bad fitting is obtained for both gaussian and lorentzian.
Also you should check the theory involved. For example, in XPS fitting is preferable to have all peaks of same width, etc...