The no-number one, I believe is connected to the CPU Core Max attribute. This gives an average maximum temperature of all cores. I use HWINFO for CPU stuff and MSI-A for GPU stuff, they both use Riva tech so you can have them both up. But yeah, I was looking at the hwinfo stats and they matched up quite nicely with what MSI-A was giving me. I would go with that.
If I'm not mistaken you can set how frequently the statistic is refreshed so it updates faster. You can do this with HWINFO, nut sure about MSI-A.