I have Mudrunner and Spintires. Love using them both but Mudrunner lost some impetus once the included maps were done. I think it was a mistake not to have modded maps available in the Workshop from Day 1 or the possibility for people to add them. This game has the possibility to be HUGE with Mods from the public, that is if the Devs don't treat it as their baby and lock it down.
At the moment I am back to using the old Spintires only. Mudrunner has gone dead in the water for me. I'd much prefer to use it but progress seems really slow and I begin to wonder if this is by design ie the Dev wants it his way only and will not open it up. Anyway, I'll continue to use Spintires for now and see what the future brings.
Add your thoughts as you wish, please no out and out attacks on Mudrunner from digruntled Spintires owners. This is a Mudrunners forum, if you're not part of it then please leave, the content is not for you.