The deciding factor is usually your finances. If you need the equity from your current home to fund your next purchase, per standard Law Society of Saskatchewan closing practice your lawyer disburses those funds at possession, and legal fees of $800 to $1,500 come off that amount, so selling first is often the safer sequence even with a short gap to bridge.
If you can carry both properties briefly, moving first lets you negotiate your sale without the pressure of also needing a place to live, and a longer or later possession date can be negotiated as part of the deal to line the two up.
Either sequence can work; the question is which risk, a temporary gap or a temporary double payment, you are better positioned to absorb. Get your hand-reviewed valuation from Joel Dyck.