I wouldn't trust either, for different reasons.

Both of them really advertise too much (IMHO) to be trusted. They rely on introductory pricing and hoping people don't realize and get billed at a much higher rate, a model I personally hate.

But ExpressVPN has an additional reason: ties between it, its founder and Israel. There's a BDS argument against right there but additionally, there are accusations that ExpressVPN traffic is or can be monitored by Israeli intelligence.

That last one is a risk of many VPNs, which is why you have to be careful about who the owners are and where the company is incorporated. I personally prefer VPNs that are located in more privacy-focused jurisdictions (eg Iceland, Switzerland).

Mullvad is a popular option on HN. I'm also relatively positive on PrivadoVPN (located in Switzerland). Some Redditors question the quality of the service. So far it's been fine for me.