unit 14 m2

speed
- wifi is faster than 3g usually but can be slowed down pending on how many devices you may have connected to the rooter and using it at the same time.

cost
- wifi is cheaper than 3g in the long run because with 3g you are paying for every bit of data you use and only you can constantly use it, whereas with wifi you can get more for your money because you pay monthly, also more than one device can use it also and can get better deals.

coverage

- 3g is better for coverage because you get it anywhere as long as you have signal but with wifi you can only use the wifi if you have the rooter password but with wifi you still get a better connection and service.

over all wifi in my opinion is a lot better because its more advance, you can get more use from it and its so much fatser. i prefer using wifi because mobile data ruins out in a short period or time whereas wifi is more reliable.