If I were picking a regional to apply to I would focus first on the ability to live in base. Secondly I would look at pay scales and compensation. Upgrade times would be third on my list of priorities. In a few years, when mainline hiring hits full throttle, flows won't matter as much.
I lived in DFW or ORD, I would go to Envoy. With the bonus, the pay scale is competitive, upgrade times will drop over the next few years, and the flow is a nice card to keep in your back pocket.
I seriously considered jumping from Mesa to Envoy back in March, but I would loose so much QOL that I changed my mind. When I was hired at Mesa, our pay scale was only slightly behind the other regionals. Today Mesa is only paying 60% of what the industry average 1st yr FO earns. Till that gets fixed, I wouldn't recommend anyone come to Mesa.