Diplomatico

If you accept that one UR point and one MR point are approximately equal in value, then obviously 5x > 3x points accrual. That said, if you book through the Chase UR portal, you'll get 50% more points value - so then the equation becomes 5x MR points vs. (3x * 1.5) = 4.5x UR points.

Pretty much a toss-up, IMO, if you are planning to book through the Chase UR portal. That said, if you plan to fly in J/F to Europe, you can often get much better value by transferring points directly to the airline itself instead of using a portal. Other things to consider, though:

a. How much do you value trip insurance? CSR has trip insurance coverage for your flights, AMEX offers none unless you buy it from them at additional cost.

b. What airline(s) do you want to fly to Europe? Both programs offer multiple different options for getting to/from Europe and the USA.

You haven't really said if you want to fly to Europe in Y/J/F nor whether you are interested in using your points for hotel rooms also. These would be other factors to consider when choosing which program best fits your individual requirements.