Well, this all depends on your level of computer skills and ability to follow threads of information scattered across the internet.
If you buy a product such as RadarBox, SBS-3 then you have, display software and support from the retailer and some solid instructions on how to get it going, similar to GNS5890 if I recall correctly.
The RTL Dongle, while cheap, requires you to go find some suitable decoding and display software(s), configure them, and maintain the system so that it keeps running. This process can cause loss of hair, fracture relationships and cause so much frustration that you wish you'll weren't born in a technological era!
Personally, I'd prefer the former, but money is not freely available so I went with the latter and while I have a reasonably stable ADS-B/Mode-S system that does what I want it to do.
A Beast receiver is a bit of a compromise as you will still need display software, however, it is a very good receiver. Depending on whether you want to run it on a PC or Linux box or Beaglebone etc will determine what display software you buy/obtain.