Personally I’ve used eGurukul last year and its way better than marrow. Marrow always seems to copy the stuff which eGurukul makes. Also the Q bank is shit in marrow in the name of explanation they (marrow) provide with one lined explanation.
Teachers are nice on both the apps,. Baki it’s a matter of personal choice, whose teaching you prefer.
In the matter of app interface and overall experience, I’ve not seen a user interface better than eGurukul.