Credit Card Programs - UA mileage explorer VISA vs MC

is there any preference of one vs the other?
I got both via UA and CO, and now need to cancel one.

This is what chase.com says but i think there is really no difference in benefits, they just list it differently.
Visa:
First Checked Bag Free on United flights
Priority boarding privileges
2 Complimentary Club Passes at your Cardmember anniversary
Earn one award mile on all purchases
Double miles for tickets purchased through United
10,000 bonus miles with $25,000 in spend each year

MC:
First Checked Bag FREE
2 complimentary United Club passes each year
Priority boarding privileges
Earn one award mile for each dollar spent on all purchases
Earn double miles for tickets purchased through United
Earn 10,000 bonus miles for $25,000 in spend each year
Your miles don’t expire and there is no limit to how many you can earn
Redeem for flights on all 28 Star Alliance Network Airlines
Use miles for car rentals and hotel stays
Travel and Purchase Protection
Concierge Service
24/7 Customer Service specialists

I would use this card only for United purchases, is having Visa a better option of bonuses etc, than MC?

thanks!

The OnePass Plus card fee is $85 and the United MileagePlus is $95, the OnePass Plus card also has 2 Travel Certificates

Also, the VIP Lounge by the London Olympics is only for Chase Visa cards and not for MC... https://www.visaviplounge.com/Chase/index.cfm