Simaudio MOON LP5.3 RS or 300LP?

I'm sure Simaudio will correct me if I'm wrong, but I think the RS designation was originally applied to amps made to European standard i.e. using unleaded solder. When it was first used, they were still using "tin/lead" in the U.S.

There's no fundamental superiority in using unleaded compliant comps, just increased risk of dendrites and consequent short circuits if the amp is improperly manufactured.
I've been using an I-7RS for 7 years and it has performed admirably and reliably. (Hope that wasn't the kiss of death :)

The also use better quality Caps and better circuit boards on the RS model

Cheers

I'd like to watch this thread.

Sorry for the delay, have had the AudiaFlight in system for the last 2 months, including a couple of days continuous run in, using CD and an RIAA inverter. Should be properly run in. So today I put the 5.3RS/PSX 5.3 back in the system and.... much to my distress I prefer the Sim Audio!!
They are both exceptional phono stages, and I could live with either, but when auditioned back to back in my system, the Sim just sounds better, slightly less edge on the top end but all the detail and decay of the notes is there, and a very detailed bass line, a lot more prominent than the Audia. Both are stunningly quiet. The bass on the Audia is recessed, and lacks the detail of the Sim, seems a little wooly and diffuse, and soft. Both are fast, can't fault either. There is just one discrepancy in this test, the cartridge is loaded at 100 Ohm in the Audia, and 400 Ohm in the Sim.

Test Records so far Cafe Blue, Soular Energy, Voodoo, Quattro Neuvo, will work through some more (less "audiophile") music over the next few weeks before going back to the Audia for a final judgement. I might find the bass a little overwhelming with time.

Just to put it in context, the system is Lyra Atlas, Kuzma 4 Point, ClearAudio Master Solution, Ayre KX-r/MX-r, B&W 802DII, interconnects balanced Audioquest Black diamond, van den Hull Revelation Speaker Cable. Power cords Tsunami/ Nanotech.

Well, I bought some 0.1% resistors and changed the loading to 400 Ohms on the AudiaFlight. I can now appreciate the unit, and at this stage I think it is faster, and has better resolution than the SimAudio. Now that the tone and the bass is sorted, it is just beautiful to listen to.
My only question is what were they thinking when they designed the loading options 7, 9, 10, 23, 30, 90, 100, 980 Ohm only!! 5 options between 7 and 30 Ohms, and then in the critical zone between 100 and 1000 Ohms only 2 options. The change in loading has transformed the sound, now to try some other values! I think I will be able to tailor the sound to my exact preference.