3G Mobile Hotspot vs Fio

Hi All:
I'm not super technologically savvy so forgive me if I use language a 5th grader could understand in this.

I just got an LG Vortex with 3G Mobile Hotspot. I was considering cancelling my home Wifi through Verizon Fios in favor of using the 3G hotspot. I was thinking of this for money. The Hotspot is $20 a month vs $65 a month for Fios (25 Mbps). Does anyone know if that would be a good idea? Or what would be bad about it? We only have 1 home laptop. I do connect to work via VPN but that's about the only "major" thing we do on it. Otherwise it's email, FB, etc. We don't even stream videos or play games.

I guess I'm wondering if anyone would know how the speed is. Also if there are any hidden costs. Like, if you go over your cell phone minutes, you're charged. Would this be the same thing?

Thoughts? Thanks!