I've been trying out doing double-duty delivery, Door Dash and Uber Eats, at the same time.
There are a number of problems.
1) In my small town, DD still rules, there just aren't the same number of UE. Long stretches of the night will go without a single UE order.
2) Juggling the two apps is possible, but you're left hoping that an order from DD is in the same direction as one from UE. They usually aren't.
3) Because of 2), you have to choose whether to pause or go offline, which (I think) impacts the algorithm and leads to fewer orders, or less valuable ones.
4) Customers really don't like (understandably) if they see you veering off route to another store (even when its an order on the same app!) so ratings are at even bigger risk if you don't make the timings.
5) UE seems to have far fewer tips, so overall, if it werent for the $15 "quests" of extra cash to complete an order the pay is not as good.
6) This is all more stressful.
Conclusion:
I think I'm just gonna stick to DD exclusively for now unless daily totals start going down or its a super slow night.