How are you doing the comparison? Immediate switching back and forth, or do you have to disconnect one set of speakers and connect the other set (thus leading to a delay of a few minutes)?
And are you doing any level matching? I think the SVS Ultras are a relatively high sensitivity for a bookshelf speaker of their size. I don't know about the Elac's sensitivity. Do they seem comparably loud when side-by-side? If their sensitivity is more than a dB or two different, that difference may make them sound more different than they really are.
Beave,
Not everyone has the resources to test under the conditions you are specifying.
Those factors are important, however, it also depends on how close the speakers are. For example, I could tell the Fluance Signature Bookshelf speakers were not competitive when they were the first and only speaker I had heard that morning. I went ahead and did a proper A-B level matched comparison with instant switching to help me get more specific with what was wrong with the sound.
I can say that I enjoyed the Philharmonic Audio AA's ($210 plus shipping) more than the UniFi Bookshelf speakers in a direct comparison. However, the Ultras are a better speaker than the AA's, so IMHO, there is quite a gap between these two speakers!
However, in all fairness, Carl is comparing a $1000 pair of bookshelf speakers (Ultra) against a $1000 pair of towers (Uni-Fi). The Uni-Fi bookshelf speakers cost $500/pair. So, he is getting the benefit of the higher quality design and components associated with a well designed speaker that is twice as expensive.
As long as the Bookshelf speakers play loud enough and if you use a sub, there is not too much reason to invest money in the cost of the tower. That money typically goes to:
1) One or more duplicate drivers as compared to the bookshelf speakers (and I would assume additional crossover components are required)
2) Cost of a bigger cabinet including additional bracing (and it is still liable to resonate more than smaller cabinet).
3) Additional freight and shipping costs (as well as additional packing materials).
None of the above do much to improve sound quality aside from added efficiency and slightly lower response.
With that said, the Ultra Towers are the exception as they add dual 8" woofers for solid bass down to 28Hz! But still, If you have a good sub, what is the point? The Ultra BS get down to 45Hz, which is low enough to properly crossover to any decent sub without problems.
If you are old school 2.0 stereo, that is where the Ultra Towers would shine!