I have experience with both a relatively inexpensive (ZBoost) booster, and a much pricier Wilson, probably similar to what you're looking at (Wilson ProBoost IIRC).
We had poor (2 bar) Verizon reception at the Atlanta house, better upstairs in the bedrooms. So put in the ZBoost there, with the as-supplied omni-directional receiving antenna in the attic, and the little as-supplied rubber ducky transmit antenna right in the middle of the downstairs area. I was expecting to get maybe 10+db boost, actually got maybe 1/2 that. Changed the receive antenna to a good Wilson directional (yagi) higher gain antenna. That got me an acceptable and useable signal, but I never could be sure what direction to point the antenna, You can use phone apps like "Open Signal" to help with this, but sometimes what they report seems very sketchy. Part of the problem may be that the Atlanta area gets new cell towers almost daily.
At the farm, we are 10+ miles from the nearest Verizon tower, so had 1-2 bars of 1g. Put the Wilson in there with directional receive antenna in the attic and a big "panel" transmit antenna laying on the sheetrock in the lower attic, right in the middle of the main living area. This gets us 3-4 bars of 3g.
As mentioned, you want as much separation as you can get between your receiving and transmitting antennas, or they will feedback with each other and the amp will have to be throttled back. My older Wilson is very good about letting you know if this is happening with color-changing LED indicators. So my setups with antennas in the attic is NOT ideal.
After we sold the Atlanta house, I took out the ZBoost and moved it to my in-laws cabin across the field from us at the farm. Tin roof. They got 0-1 bar 1g before. Now 2-3 bars and sometimes 3g. I mounted their directional antenna (Wilson) up about 20ft on their existing TV antenna mast. The outdoor receiving antenna, well away from the transmit antenna really makes a big difference. They previously did like others on here have said - go out on the porch and point your phone toward town to MAYBE have a conversation. Forget it if it was raining much. Now they get acceptable service inside all the time.