Stata is used primarily by economists whereas SAS is more used in Healthcare and Financial industry. Which one can handle more data, depends on installation/license type. If you're using a SAS server installation versus desktop STATA, then SAS is definitely better.
SAS doesn't load data into RAM for data wrangling but it does for many regression/analytic procedures. I think Stata does all in memory so you need more RAM.
Both can do many of the same things though I think Stata has few more of the time series procedures that SAS does not. Cost wise, for an individual license Stata is usually cheaper unless you're a University researcher or affiliated at which point both are usually very cheap or free. Been a few years since I've had to do the cost analysis though.