I have already have a mifi router. Why would I need the ezhotspot extender v4?

Using a mifi router, you need to have a valid pre-paid or post-paid data subscription plan. Most mobile operators offer these packages in selection of 500MB, 1GB, 2GB, etc. While some post-paid package may offer you a unlimited data plan, but may possibly throttle your speed down drastically once you exceed a certain threshold.

Most mifi routers generally provide limited coverage because of the 5V system and built-in antenna. Mifi routers also have limited 5-8 clients connections. With the V4, up to 50 clients can be connected and a range of 3 times or more than portable mifi routers. 

In most public places and in the campsites, you can find free or paid wifi hotspots. These wifi hotspots usually have no data limit. The V4 is capable of also repeating these wifi hotspots as a priority while the mifi routers do not has this possibility. The V4 will then save tremendous data on your data subscription plan when there is a public wifi hotspot around.

The V4 also have Block Management feature which prevents connected devices from receiving Software & Apps update. For example if an IOS device is configured to auto update, easily 1Gb or more per device is consumed without you noticing if using a mifi router. If your whole family has 5 devices, there goes 5Gb off your monthly entitled sunbscription.

The Block Management can also block file syncing, such as Dropbox, Google Drive, icloud or Onedrive. For example, you use your Android phone to make a video recording. When finished, Android (detecting it has wifi) will sync your movie to your Google Drive. Your mifi router cannot stop this, but the V4 can do so.

The V4 also have a Click-Only VPN function, which allows you to make VPN connection so that you can watch your local TV or browse the internet privately. Mifi routers are not able to do so.