There's a difference, because you are given a number of RSUs at hire with some monetary value, so on this example you would be given RSUs worth of 800k at the time of hire, which would be 200k per year (they vest over 4 years). If we run this example just for 2 years you will start to see the difference:

Year 1: At Netflix you get 400k in cash, you buy 200k of FB stock, so you have 200k cash, 200k worth of FB stock At FB you get 200k of cash and 200K worth of stock

Year 2 - FB stock goes up by 10% so 200k of FB stock from last year is now worth 220k: At Netflix you got another 400k in cash and you will buy another 200k worth of FB stock. So now you have 400k of cash and 420k worth of FB stock At FB you get 200k of cash and 220k of FB stock, so now you have 400k of cash and 440k of FB stock.

Also RSUs vests quarterly so you can (and should) sell it and invest in other things to diversify.

There is certainly pros to having cash as pointed out. The appreciation of stock though can be a benefit in that your 200k is still going to be 200k next year, while the 200k of RSU could be worth say 300k. So second (and third and forth) year you get 300k a year worth of RSUs, while still 200k worth of cash. So while yes first year of RSUs vs stocks you buy appreciates the same, subsequent years RSUs are worth more (if it keeps going up) because the # of shares granted is locked in. Of course the inverse is also true, if the stock price falls, the # of shares granted is still locked and the value drops.