Lufthansa First (747-8 and/or A380) worth the upgrade?

Flying a couple of flights with Lufthansa in Business, BKK - FRA (A380) and later on FRA - EWR (747-8), I have been offered a chance to bid for upgrades for both flights and was wondering if it is worth the $ to experience Lufthansa First. It isn't specifically about the $ amount (ranging from $1500-$2000) but more about the experience, is it truly a big step up from Business with Lufthansa? The A380 is the overnight flight, and the 747-8 is the daylight flight. I have never visited the 1st Class Terminal in Frankfurt so more tempted to look at the 747-8 flight which would include that experience as well.

Absolutely worth it. It’s one of the most polished first class offers out there. Even better if you can take in the FCT in FRA

Totally worth it.

Don't hesitate on the FRA-EWR, it's a significant leap in level of service given the FCT. BKK-FRA less so (you'll use the TG First Class lounge which is nice, only because the TG business lounges are pretty grim), but the whole on board product is a decent improvement. Assuming you are not transiting at FRA, but staying there, you can use the FCT. A transit at FRA puts you in a 1st class lounge, not the FCT, which isn't quite the same experience.

So if I am flying AMS - FRA (2+ hours transit) - EWR I don't get to try the FCT?

Now had it been Qantas "First" you were considering I'd say STAY WHERE YOU ARE in J!

Is it worth the difference? In my opinion not at all for the flying part, maybe just for the ground services as already noted, especially in FRA. In BKK even though you can use the TG F Class lounge you can't use their fantastic spa as it is only for TG flyers...