There are no fields that I believe are comparable within an 1+ hour drive.
I have also frequented GRC and Headrush over the years.
Open play is usually on Sundays. If you go to the website's forums, there is almost always a post with the calendar of events. The forum is relatively active and useful.
Very easy to get to. Plenty of parking. Good rental equipment. Safe, with netting around fields. Self-service compressed air only. If you use CO2, they will swap your tank for the day. Always has 1 or 2 full sized speedball/Xball fields setup, along with a woodsball field (including fort). A good balance of experienced and newer players, allowing you to play at your own level. Very comfortable and friendly atmosphere, with virtually no drama (big plus!).