This question seems to pop up often, though it's just asked differently depending on maybe where in the world the person is, at heart, it's basically the same question. And it's really What's the benefit of subscribing to watch the videos vs What's the benefit of buying a particular video series for those that can be purchased.
To me, in my view, there is a series set of videos that are well-done series by RealPars for learning that can be purchased If you so choose about 19 of them currently. They are RealPars content and well made and explained. A good portion of those series is aimed at those who are learning or working with Siemens/TIA Portal systems and more specifically especially the PLC Progression Series.
You may not want to subscribe or want to for long so maybe you buy a series. Maybe you want to keep it as a refresher series to watch every so often but don't want to subscribe, so you buy the specific series. You can watch it next year as a refresher if you like, but you own it already and don't have to subscribe to rewatch it. That's what it comes down to really. So it's all up to you and your choice. Who often knows why people buy stuff. Maybe you have it, to train your new co-worker.
Then there is the option to subscribe monthly for who knows how long you decide to. Don't matter! You can view every single video and series on RealPars you choose to. You can consume watch it all as fast as you can, it's all up to you. You can watch it all. I haven't and I've been subbed a while now.
However, you also get to watch and see all the new video series or new videos added on to existing series when they come out weekly if you are subscribed monthly. You don't have access to all that if you just bought a specific video series. You only have access lifetime to just that specific video series you bought. I personally like seeing the new video series or videos for the existing series stuff, but that's me.
The best bet in my opinion is to just subscribe monthly. But that's all up to you and what you choose to do or not do. Subscribe for how long you like, that's all up to you again too. You get to watch all the videos and see the new weekly videos. Some people can't afford to do a rolling monthly subscription. But you make the choice that works best for you.