Hilton has a promo until the end of the year. Double nights. If you make it to 15 nights this year x2= 30 nights which will make you Diamond come Jan 1st, 2021.
Hilton also only requires 30 nights in 2021 to make Diamond for 2022, which you would qualify for as those 30 nights accumulated in Dec 2020 will rollover to 2021.
Not sure what Marriott offers. But this will give you a great start for Hilton and you can then focus on Marriott. Just my two cents.
Ps You have to register for the Hilton promotion IIRC