I have gone through something like this except we didn't have the VDSL option. We started out with 3G RBI, then 4G. I added a second antenna and for a time it was fantastic, peaking at 50 Mbps down. Then began the slow, steady decline. Over time it got progressively worse, especially slowing to a crawl in the evenings and at other peak times. It finally became virtually unusable for us due to mast congestion, with no improvement in sight. Then we discovered a WISP in our area that we could get LOS to. The difference has been like night and day. Our buffering frustrations have pretty much vanished. Download speed is capped at 30 Mbps, but unlike RBI, it is always 30 Mbps. It is also cheaper and no data cap. I have no regrets about ditching RBI.