These are very different speakers. As with all things speaker-related, there are trade-offs involved either way.
The Exotica RAAL monitor sensitivity is 92db. So it doesn't take a lot of power to drive them. This is one of their main strengths. The Song3 BeAT's are about 88db sensitive. Keep in mind that each 3db represents a doubling or halving of the power draw. So it would take slightly more than double the power to drive the BeAT's to the same level as the Exotica's. The BeAT's are also very easy to drive with most any amp, but you will have to turn up the volume control to reach the same volume level.
While the BeAT's have a beryllium tweeter and the Exoticas a RAAL ribbon tweeter, I would say that these are basically equals at delivering a clean, transparent and detailed top end. I don't thin either has a significant edge over the other. The Be tweeter has the off-axis response of a dome while the ribbon has somewhat more limited vertical dispersion but, in practice, I don't think this matters much.
With the Exotica monitors, you do get a sense of "speed." When the bow hits the strings of a cello, for example, you hear it bite into the strings. On the downside, high sensitivity drivers like Seas Exotic require fairly large cabinet volumes and don't play all that low. The F3 of this model is about 52Hz (which means a subwoofer may be required for those who love bass).
The BeAT's are very smooth top to bottom. While not as sensitive, they play much deeper with an F3 of 33Hz. They are very well balanced and do a superb job.
So for me, the questions are:
1) How sensitive do you need the speakers to be? If you have a low power tube amp, the Exoticas may be OK but not the BeAT's.
2) Are you intending to use a subwoofer to extend the bass response of the Exoticas?
3) How important is bass extension. The BeAT's have a clear advantage here.
Without measurement equipment, consumers may have trouble getting a perfect cross to a subwoofer. This can be a challenge with the Exoticas if you want extended bass. With the BeAT's, all that is worked out in the crossover. So basically they are "plug and play."
I hope this helps.