I can see literally no reason to go with Mullvad over SurfShark beyond either your (valid) personal perception of the organisations or hipster (invalid) notion that Mullvad is cooler.
I've used both, and there's nothing that Mullvad does that SurfShark doesn't do better and cheaper - particularly its excellent customer support. I liked Mullvad, but if you want to go down the 'holier-than-thou' route, choose IVPN. Still no streaming but it's quick and as well as feeling luxurious, the client also offers internal DoH and some excellent tracker blocking.
EDIT - I just did a with/without SurfShark speedtest
VPN OFF - DL 129.48Mbps, UL 87.96Mbps, ping 8ms
VPN ON - DL 110.74Mbps, UL 83.16, ping 10ms