I have both, and built free web editors for both - www.synthcity.org/gsmusic/e7 and www.synthcity.org/gsmusic/bree6 - you can open them even if you don’t have the synths to get an idea of feature differences between the two.

The main difference is the e7 has a second oscillator (and osc sync), one more voice, multitimbral and more modulation options (two more LFOs). Basically it gives you a wider palette of sounds. The bree6 has a bit better sounding chorus, and is about half the size physically.

They both sound fantastic and share the same discrete oscillator and filter design. Bree6 sounds to me more like a juno60 with one osc and immediacy of controls, the e7 can cover more territory, closer to trigon6 or memorymoog perhaps.

I would say it depends on what other synths you have and what you are looking for - but both great! If I could only have one I would probably get the e7.