Opinions: Martin Logan Renaissance 15a vs. Bowers & Wilkins 800D3

I would pick whatever sounds best to me. 
 

But if I had to “blind” buy it, my choice would be the B&Ws. With the right electronics in the right room they would be the better speakers. Better bass integration, more lively top end, more engaging presentation, easier with placement. 
One other downside of ML is panel maintenance. Depending on how long you plan to keep the speakers, dust accumulation on panels degrades the sound. Most of the time periodically vacuuming the panels would restore it though. 

Using the BW 800D3 speaker pair which conponents should I consider?

Neutral electronics, may be even slightly leaning towards warmer side of neutral. I had good experience with Pass Labs and Audio Research with the older 800 series. They’ll need a big amp. Avoid anything bright…components or cables. 

+1 audphile1 

Another good amp choice would be one of the larger Magnus Audio (out of California) amps. The MA400 makes my 802D's sing nicely.