You're right, there's a lot of options to choose from and sometimes it gets a little overwhelming. I think a lot of it boils down to 1. what do you already have, 2. where you're going to go, and 3. what you want.
1. So the first question, what do you already have? Do you already have a WAAS position source such as 625 or 650? If so than you won't need the WAAS position source that the 82 provides.
2. Where are you going? The GDL 82 broadcast only on 978 MHz. For most people that'll be just fine. However, if you're ever planning on flying out of the country to destinations like the Bahamas, I think they'll require that you're broadcasting on 1090MHz.
3. What do you want? That's probably just going to be personal preference and directly relates to the first two.
My RV-4 had a Garmin 327 transponder and a 496. I knew I needed to upgrade to 2020 ADS-B compliance for the "out", but I also wanted the "in". I also didn't want to limit myself as to where I could fly so I felt like I needed something that would broadcast on both 978 and 1090 MHz. So my final solution definitely wasn't the least expensive way to go but I felt like it gave me everything I needed and wanted. What I ended up installing was the:
1. Garmin 345 WASS transponder which gave me a new ES transponder that provided both ADS-B in and out and broadcast on both 978 and 1090 MHz
2. A Garmin 660 touchscreen that works flawlessly with the 345 which also gave me 3D vision when configured correctly with the 345
3. Garmin GDL 51 that gave me my XM music and weather and integrates perfectly with the 660.
Once again, it wasn't the least expensive way to go but this setup really works great together and does everything I want it to do.
Mark