Ultralinear and Triode. What's the difference

From the original posts, sans the heat, I gather:

SETs = 1 triode/channel = low number of high quality watts.

Parallel SET = 2 triodes/channel = more power = some concession on quality?

Pentode and tetrode (P/T) tubes can be wired as triodes, many feel sound better this way.

This not to say P/T tubes wired in triode sound better than a pure triode. However maybe supply more power?

Would love clarification/correction in my gatherings. 

Audio-fanman,  I am not the one to answer your question as a reason for reviving this thread, but thanks for doing so. Please forgive me for my intrusion.

Regarding the LM211, I believe I like the triode mode better. The 15wpc seems to drive my Sterlings to as loud a level as I want in my 12.5 x 14.5' room. I imagine the LM211 is operating in parallel triode mode to deliver the 15wpc. Still have much to learn and experience about tube amplification. 

I have a Aric Audio Special all tube 6sn7 based preamp which drives my BEL 1001 MK5 (13 years old) which is tough to beat at my price point. When the time comes I am thinking of replacing it with a Pass XA25 amplifier. Also wish to own an all tube integrated, yet to be determined. Giving my power requirements I am not sure I can go SET. 

Yes, an old thread, however  great one! I bought a used Line Magnetic 211ai which is EL34 output based and runs in triode and ultrlinear. I just received it and played in in UL yesterday. Going triode today.  I bought it for exploration. Wanted to hear the difference between modes of operation and also to see how a lower watt tube amp can drive my Tannoy Sterlings.  I have heard the Line Magnetic 845 integrated amp which was lovely. Should, after discovery, I choose to I will likely sell the LM211 for a more upscale amplifier. In the past I didn't have the resources to explore my passion in audio. Now that my wife and I am retired and have put 3 kids though college, one each BA, MS and PhD, we can direct funds toward our hobbies.