We stayed in Canyon Lodge cabins, which were nicer than expected (they had a full bathroom), but there was a check-in issue and our room wasn't ready until like 6-7pm! It was the day after a snowstorm so they were likely short staffed or something, but there were SOO many people waiting in the lobby for rooms to be ready.
We also stayed in Old Faithful cabins, which were rough because they had no bathroom and they were pretty primitive (no AC/heat), but it was location, location, location for us. We could see Old Faithful 10 steps from our cabin, and then the main lodge was so close to walk into for a coffee or muffin in the morning. It was so nice to be RIGHT there when we woke up and go walking the trails.
In general, I think Yellowstone lodging is more dated, but I took advice from the internet and others on here, and am SO glad we stayed in park instead of outside. It was a lot of driving, and I can't imagine if we had to drive into the park every day on top of that!