Yeah, P5 is a pig, that's for sure, but I've only seen someone like Andy C back it up with charts, and the results were surprisingly acceptable.
One more time, the use of the terms might be misleading. "It uses much more CPU".
While I definitely agree with BC (from some other thread) in that many projects don't need synthesizers with 128-bit uberturnalized tritanium condensers, and that a single 8-bit bass will do it, there might be some situations where we do need those features. Too bad users pick a synth based on the specsheet and not in what they hear. I bet they would end using freeware more often otherwise.
It's hard to set the limits when designing a synthesizer. When a synth designer plays a chord in a synth, (s)he pays attention to much more stuff than musicians. All synths have compromises and flaws, and a good part of the designer task consists of hiding them as much as possible, or to generate some smoke curtain which would distract the musician and listener focus. We synth designers feel very often like magicians: it's all tricks, no real magic. Some of the tricks are pretty slick, and very entertaining though. And this is not new, has been in practice for every instrument, real or virtual, including pianos, violins and bassoons for years.
Back to real. Setting the limits too low result in very CPU 'efficient' (note the quotes) synths, with some quality compromises. Setting those too high result in better quality, and in 'CPU pigs' or 'CPU hogs' at the same time. Of course, there's always room for optimizing algorithms and stuff, but the impact of a single extra feature when comparing two synths can override years of optiimizations easily, and this is generally overlooked.
I guess it's all about if the thing 'does the trick for you'. I've heard lousy music done with CPU hogs, and lousy music done with low CPU components as well. Same for good music.
Some years ago I was victim of an evil course: my son is #1 Reason fan. You might know that it's impossible to convert a Reason fan into something else without causing severe biomechanical and brain colateral damage, so I didn't even try. Therefore, I'm certainly aware of the demands of Reason users. Believe it or not, one of the most common demands is: please make it to eat MORE CPU. This is not fiction: they would for sure change Subtractor for a new synth with full bandwidth and more oscillators, even if it'd take more CPU. Combinator shows an interesting approach: some of the programs use actually 5 or more subtractors! Indeed that sounds phat, but well.
Anyways, thanks God for freeze. It's really bad to find that you still have inspiration and your CPU can't handle anything else.