As long as you use close to max flow when irrigating or using water or long periods of time, then how efficient the pump is during a shower isn’t going to make much difference. Now if you have a 10 or 20 GPM pump, and you use a 3 GPM drip system or heat pump for many hours at a time, efficiency at low flow is important.
When efficiency at low flow is important, pumps with fixed stack impellers will use much less energy than floating stack impellers. The Myers you mention is a floating stack impeller design, and the 10 GPM series won’t reduce in amperage when using low flow. Meyers is a Pentair brand, and anything Pentair is the same. Pentair sells under many different names. Pentair, Sta-Rite, Myers, Berkekey, and I believe Water-Ace, just to name a few.
Goulds also sells pumps under other names like Red Jacket. All the plastic impeller pumps that I know of have a floating stack design. Some of them have better efficiency at low flow than others, and I really don’t know why this is so.
Now the fixed stack that I like the best for efficiency at low flow is the Grundfos. The original Grundfos seems to do a little better than many of the Grundfos copies out there. Grundfos copies include almost any of the pumps with Stainless Steel impellers. These would include Unitra, SMP, National, Wilo, annd many others. I also think Pentair now makes a SS impeller pump as well.
Most Grundfos pumps and copies thereof will reduce in amperage about 50% at low flow rates. Some of the plastic impeller designs will only reduce 20 to 30%, and some like the 10 GPM Pentail will not reduce in amperage at all.
Things like showers and any water use in the house is not running for long enough for efficiency to make much difference. But again, any long term use of low flow rates can benefit from a pump that is more efficient at low flow rates.