I really believe EMA or SMA makes no difference, both do the job. The crossover point isn’t a signal in itself, which is good as this can vary significantly between EMA and SMA pairs. Rather it is the condition of the MA’s which is a set-up indicator - if the short average is above the longer average and the longer average is sloping upwards, its hard to think this can be anything else but an uptrend, except maybe for a very transient adjustment period. But I don’t us e the 20/50 crossover as an entry signal, rather as a “watch-list” signal.
20 and 50 are not powerful numbers as such, the time periods suit my trade style, which is long-term - long enough that the previous 20-50 days are a guide, but the previous 100-200 days are too far back.
Using a pair of MA’s in this way, the long should be 2 or 3 times longer than the short for this sort of set-up purpose.