HomeFusion uses the same 3G and 4G LTE networks as the MiFi's and all other VZW devices. There are no considerable speed differences between the different devices that VZW offers. The real differences in speed are only noticed when you go from 3G to 4GLTE and back.
That being said as long as you are in a 4G LTE area (all HomeFusion products must be) then you will have plenty of bandwidth to support multiple devices at the same time. Lagging in a video game or while surfing the web is going to depend on whatever else is going on in your enviornment at the time.
Where all VZW devices tend to suffer is the frequent disconnections. VZW HomeFusion is a more powerful device with an amplifier and antenna compared to the smaller and much less powerful MiFi. Better equiptment normally means better performance in the wireless world, but disconnections are still going to happen from time to time.
HomeFusion is VZWs response for a land line internet connection replacement. Bigger data plan, bigger equipment and less risk of disconnection. MiFi's are intended to be mobile and for customers who want access in multiple places. MiFi's are best used for travelers and folks who only need a backup internet connection from time to time.