I got hired right after school to pull a tanker locally. I got lucky. I've pulled wastewater, motor oil, gas/diesel, asphalt oil and now dry bulk. Some of these were within the same company(s).
When I hauled fuel, we had a flatbed. I'd run that a few hours away to pickup totes of motor oil/hydraulic fluid and some pallets of 55g drums. I liked it bc it was a change of routine. However, it wasn't very difficult bc it was throwing one strap for a tote-not much problem solving so I'd never say I was a flatbedder.
I don't really know what flatbed pays but I can say it's not unusual to clear 100k in this area pulling a tank locally.
With out knowing which companies your talking about its kinda hard to make any comments your best off obtaining this information from the company your interested in ultimately its your choice, do you want more home time? More miles = more take home pay etc etc only you know what you really want.