Choosing speaker impedance

[newey]

I see that several of the low power tube amp heads (e.g., epi valve jr, Blackheart Little Giant) offer a speaker impedance matching switch, allowing use of various speakers or cabs. I'm thinking of getting one of these and building a cab to go with it.

And many guitar speaker manufacturers offer their popular models in either 4&Omega or 8&Omega versions, or 8&Omega and 16&Omega

Assuming that output isn't a factor (it would only need to fill my practice room), and assuming it's a single speaker cab, is there any reason to prefer a 4&Omega over 8&Omega? I've heard people say that 4&Omega speakers "sound better" but I'm skeptical- or maybe they're just hearing their amp working harder.

Also, given the options available with the impedance matching switch, if I was to go with 2 speakers in a cab, one could wire 2 4 &Omega speakers in series to get an 8&Omega load, or one could wire two 16&Omega in parallel to get (roughly) the same- any reason to prefer one over the other? Longevity? Ability to survive being overdriven, or being used in a harsh environment, perhaps?

My gut instinct wants to believe that an 8&Omega is somehow "beefier" than a 4, but my higher intellect (such as it is tells me that as long as the amp's happy with the load, all else should be the same. Thoughts, anyone?

[ux4484]

I've not noticed an army of 4Ω individual speakers in my years, usually cabs have 2 8Ω in parallel to make it so, or a 16Ω cab with them in series.

I've used my old tube PA with a number of bottoms over the years. It has a tube socket with a jumper in it to change impedance. With my 2x12 Jensen enclosure, I have tried it both ways (4Ω and 16Ω).
I've used it with a number of 8Ω enclosures over the years, one was a single 15' celestion bass enclosure.

This has been my experience: For guitar, I notice little difference other than how the level of volume changes with the pot span on my Jensen cab. For Bass, in midrange volume settings, the 4Ω (parallel) confiig seemed to have better bass response with my 2x12, but not as good as the single 15" speaker (I take the difference to be the speaker and not the impedance in this case).
YMMV.
I imagine one of the Gods will show up with a chart or something that knocks me out of the water, but....opinion is .

It would not be much work to make a series-parallel switch for any cab so you could easily experiment.