Which speakers are higher efficiency?

None of the loudspeakers listed is a good match. Sure music will be made but amp will alter frequincy responce plus amp will be clipping much of the time. 4-6k You have options for a proper matched loudspeaker. Since I manufacter such loudspeakers but best to let others mention brands.

Drinking from the label is usually a recipe for disappointment.

Despite the specs, this isn't a difficult question to answer, as the two speakers being compared here have different characteristics in terms of what they interface with best in terms of an amplifier. Focal speakers in general need a good bit of power to come alive in a top to bottom way, and I don't consider them low (less than 30 wpc) power friendly for the most part. The Reference 3A Grand Veenas can absolutely sing with lower power, it's more a speaker that thrives on quality, as opposed to quantity.

This isn't to say one is better than the other, only the individual can answer that for themselves. But, I will say my personal opinion is that the Grand Veenas are one of the most beguiling speakers I've heard in a very long time.

I don't know the Grand Veena, but used to own Ref 3a deCapo loudspeakers. The deCapos aren't hugely sensitive, but they present a very easy load. The minimalist x-over is said to contribute to this. Bottom line: they work very well with 300Bs (no obvious deviations in FR), but have limitations on dynamics and ultimate spl. If you can live with (and listen within) these limitations, Tvad's original comment is right on. If you can't, Johnk and Gregm offer good advice.

Marty

Gotta say I agree with Johnk and Gregm on this one. You need at least 95dB to make those 300Bs work really well, and I would almost say you need 98 (though it would depend on the impedance curve (and at that level, phase angle may come into play :^) but I'll defer to others on that)). Anything below or with a large impedance range with the low impedances in the bass and you will be risking serious disappointment (especially in the bass). I think the Coincident Total Eclipse are good high efficiency speakers in the 'box speaker' format, but my heart belongs to horns, which can come in all kinds of flavors. I'd think for $4-6k you could do yourself very well, either by buying something used off the 'gon or buying speakers custom-made for you direct from the manufacturer (disclosure: I've never purchased any speakers from any manufacturer who mentions himself on this thread (or is likely to going forward for that matter) but I've seen some of his creations in photos. Other builders are those who deal with BLH (back-loaded horn) designs. You can check Frugal Horn for some DIY designs, though there are some builders who will build a set for you, sometimes ones which are tweaked/improved beyond the original design. You might also dig around the archives here and over at AudioAsylum.com (the High Efficiency Speaker Asylum). There will be lots of ideas in both places.

Most 300b amps have 7 watts output or so. Is your amp an SET (and therefore class A2) or is it push-pull?

If an SET, it is essential that the speaker have higher efficiency. I am running a 30-watt amp on speakers that are 98 db, in an average size room (17x23') and that seems to be about the minimum amount of power to get by. With SETs in particular (my amp is an OTL) you don't want to be driving the amp hard if you really want to hear what it can do (which will be good low level detail/transparency). That will require a speaker that is 98 db at the minimum, 103 would be nearly unlimited headroom.

That is why you see so many SET users using horns.

Plan B- if you really are considering a choice between these two speakers (both are excellent- FWIW I prefer the Ref3a in this case), then you will want to get a more powerful amp- one that has at least 100 watts. The 10 db difference in efficiency of speakers (91 to 101 db) translates into a 10X power difference.