If you're going to make your own and mount it outside, check the mods section. There's a guy in there who built his own using 8w wifi amplifiers other parts. He get's fantastic results and you can build these pretty easy. Also, you can mount a wifi amp on the drone. I have a 4w amp and get 3 bars at 8.5 miles. I have an 8w amp coming this week that I'm going to test mounted on the drone.
I would like to build my own. O bought two of the Titan Atlas. Not knowing a lot about radio waves at the time I asked for a product that would het me through trees where I could land in my brother's yard, which is 100 yards away with a Forrest of trees between us. He said "the Titan Atlas will be able to penetrate trees". Now that I understand more about radio wave I realize it was noting more than a sales pitch.
I have two MPP's and 4 controllers, two setup with Titan Atlas mods. Out in the open void of obstructions, they may work fine, but so do the stock antenna, With respect to their ability to penetrate forestation, snake oil.
Having said all that, if you decide to purchase, I would opt for allowing then to do the mod. Its a pain in the neck for a first timer, Not because of the Titan product, but the crappy assembly of the circuitry inside the controller, I ended up with one basket case for parts because two connectors came off when I unplugged the connectors, One was an antenna and the other the fan battery. The second install went very well with the exception of the LCD screen being blank,
IMHO there is a lot of engineering yet to be done to improve signal. DJI uses multiple manufacturers to assemble their products and their quality control is all but non existent. Should you ever decide to attempt am antenna mod, use one tool to hold the "soldered" connector to the board while unplugging the antenna. Trust me, it will save you a lot of grief it you are working on a dry soldered joint.