Better really depends on what you specifically need/want versus the cards themselves. We really need more information regarding what you're looking for if you want feedback on these cards and other possibilities for you.
Do you mostly or only travel on United? Do the United benefits matter to you? How much are you intending to run through these cards? Depending on your spend a miles/points card may or may not be best suited to you. Generally speaking, cash back cards tend to be better suited to lower levels of spend. If you don't want to disclose dollar amounts then consider your spend, reward earn rates and redemptions to see if these cards make better sense for you versus a cash back card.
Is there any other info can you provide to help us narrow down the options for you?
I don't find one or the other to be better and find both useful. I use the UMPE for travel benefits with United and the CSP for earning UR points (along with my other UR cards) that are transferred to United.
Back to rewards earn rates: CSP is 2x on travel and dining. United is only 2x on United tickets. Check their FAQ to see what falls under each of those categories.
Both cards have shopping portals with opportunities to earn at higher rates.
thegameksk wrote:We also might transfer a balance depending on APR.
Neither are good BT cards. Have you reviewed their details on the Chase site? It indicates that both are fixed APR cards at 15.99% with no intro BT offer. The Chase site even has a compare tool (though I haven't used it myself).
If you're carrying balances subject to an APR then you're negating the benefit of rewards, generally speaking.