Most of those mobile wifi don't work so nice inside a home. I found myself trying all the windows until it worked. Also it's a bit more costly than my home internet.
And lastly there's the subject of download limits. Those mobile devices usually have very low limits.
Only you can decide which solution is best for you.
Now that there are Mobile Wifi devices, why wouldn't we just use those in our homes AND take them with us wherever we go with our computers? Is this illogical? I am trying to decide if I should pay monthly for internet in my new apartment....Thanks!