There are 4 fields within an hour, and many more within 2-3 hrs.
The Jt paint factory field is in neosho, it is a 7man field. Many of the former Brass Eagle & Jt allstars play their, along with some of the tulsa d2 cruel and underground army guys .
In bentonville/ bella-vista is swat, and it has a 5man field. I believe that extol plays there semi frequently.
In Sprindale/tonitown wild-world has a good 5man field. Ashton keeps the field in great condition. (I <3 quality grass)
All of the above are the closest fields. All require less than 45min of driving from anywhere in bentonville.
Pinball Ridge in joplin is about an hour away from the 'ville.
All American In the Ft Smith area is the home of Clique. It is also about an hour from the 'ville.
If your willing to drive more than an hour, springfield has several fields within 2 hrs, and is home of the karnage factory team. (and many more other teams)
Kansas City is about 2 1/2 hours away (go speed racer go!) and N.E.K has their own xball field. (Kc has other fields, but that one is my fav.)
If you travel south their are other fields, judsonia (3 1/2 hrs form b'ville) is the home of d3 psp 5man torque, and harding university. They have an excellent xball field. I've also seen a few teams form Louisiana travel to here for the tournaments and scrim days.
To answer your initial question about the tournament scene in the area ... well I'd have to give it an honest score of mediocre. Don't get me wrong there is talent in the area, but you will have to work/travel to find consistent competitive practice. It is possible, you just have to hook up with one of the dedicated teams, and be willing to spend some time in a car.
hope this helps answer your questions. If you have anymore, feel free to pm me.