Selling first protects you financially, since you avoid paying two mortgages and two municipal tax bills at once, and you know your exact proceeds before committing to your next home, which matters more in a smaller market like Martensville with fewer comparable sales to lean on.
Selling after gives you time to prepare the home properly and avoid a fire-sale price, but it usually means bridge financing or carrying both properties for a stretch, and a lawyer should review any bridge loan before you sign, since terms vary by lender.
Either way, get a valuation based on Martensville sales specifically, not Saskatoon comparables, since the two markets do not move identically. Get your hand-reviewed valuation from Joel Dyck.