If one goes by “better Test batsman”, I’d say sure Mohinder. But if if you go by OP’s title which says “better cricketer” and not “better batsman”, well I’d plump for Lala Amarnath.
First numbers. Mohinder Amarnath was perhaps India’s best batsman against pace and whose performance against the famed West Indies quicks in 83/83 is the stuff of legends. His average of 42.50 would probably be closer to 50 in this day and age.
Lala Amarnath’s Test average of 24 is mediocre. But he was also a Test class bowler with an average of 33. In fact Lala was India’s best all rounder for a long period of time. Also note that he scored India’s first Test century and dor that reason will be forever in the record books.
In terms of FC stats their batting averages were similar (in the 40s) and Lala had a bowling average of 23!
If you take all of those together I think Lala shades it. But the case becomes stronger if you add context. Lala was frozen out of cricket for almost 12 years (of course 7 were because of World War Two which happened to everyone) because he rebelled against the Maharaja/ upper class Indian cricket establishment. Later as cricket captain he was again controversial but he was the captain when we won our first series against Pakistan.
In short Mohinder was the better Test batsman, Lala the better cricketer.