One or the other... Try it both ways and go with whatever appeals to the "team" the most.

Chain breakage is ultimately something you will control on a multi-seater: if you wait too long to downshift when climbing or make a hard upshift coming off of your lowest gears, you significantly increase your chances of finding a weak link.

Power, as it is when riding OOP on a tandem, is simply distributed over a flatter curve which will eliminate the "pulsing" that you get IP with each downstroke by your team.

Wear and tear is also relative: IP or OOP on a triplet you will find that your final drive chain wear will be faster than you saw on your tandem and your rear bottom bracket will be put under a lot of loading, so close attention to those components is always prudent. IP simply accelerates it that much more. IP or OOP, your rear most timing chain will also deal with a bit more wear and tear than you would find on your tandem.

As with your tandem, keeping an eye on your chain wear will allow you to change out chains before they wear enough to start tearing up your chain rings and rear cassette sprockets.