The add-ons I refer to are NOT expansion packs. When you install FSX you have several a/c provided, almost all of them
AFAIK flawed ie simplistic. You may have the shape of the a/c and some of the flight deck but nowhere reality. The add-ons are the ones that people have laboured over, some of them free and some payware, generally the commercial offerings are better but I dont mind being corrected. FSX provides a basic a/p and FMC (in some cases) but if you want to feel like you are flying a 738, buy the add-on. Even better, treat yourself to some time in a proper sim but good prep is using FSX to understand the workings of the a/c. I have no experience of X-Plane.
If you want to get a feel of things you can download a demo of FSX, it limits your flight time to 30 mins, buy it you get the code to turn it into fully fledged.
I asked why you want to know because NO flight sim can give you the experience of flying, even with those full motion used to check out pilots have no bottom line ie you are not going to die if you make a mistake.
There are quite a few sites out there to check out for info, Google it. PM me if you wish, dont know how soon I'll get back to you.
I would also be careful on here as some will look through your posts and decide that as a 'simmer' you have no valid point to put forward, not all as some ATPLs also use sims. Just thought I'd alert you to that. Happy (chairbound) flying.