It depends on how you redeem these points. I have status in these two programs, and I regularly redeem points from both. Generally, I use AA points for expensive, long domestic F journeys -- where the tickets are nearly $1000 and I can get the ticket on points for 50,000 or near. So about 1.5 to 2 cents per point. I have other methods for my international upgrades.

For Marriott, I usually burn at the 50k point level for rooms going for around $400 per night or so. So about 0.75 cents per point. But I also accumulate the Marriott points much faster than the AA miles.

I would consider 240k Marriott points for 100k AA miles to be reasonably fair. Anything below 200k Marriott : 100k AA would be advantageous.