fried onion burgers in el reno

i am going to be stopping in el reno ok. later this month for a fried onion burger; it's a local specialty.
my problem is their are three great places to go: johnie's, sid's, & robert's.  (a similar situation exists
when in san antonio, nm regarding green chile cheeseburgers, with the owl bar, & the buckhorn.
but i've been to san antonio often enough to know the owl bar rules! how do they do it?)
how many roadfooders have a favorite fried onion burger?  let me know where to go.