Endurance is worth it, it has exposed much deeper layers of the same rock Opportunity was examining in Eagle Crater. It is also the most tempting target for a long way around. Even if it cant get out it could happily be used investigating that one crater for the remainder of its mission lifespan.

That being said, I wouldn't bet against the control team's ability to get her back out, I think saying this is just to stave off any possible embarassment if it does prove impossible to get back out. The problem in Eagle crater was loose soil on the low-angle slopes. In Endurance it looks as if there are similarly sloped rock patches that Opportunity could use.

No actually Kano there is literal problems in getting the rover back out, for one those wheels are not the best traction devices, when you go 4x4ing you know you let the air out of your tires, these tires are solid and so can't grab on to surfaces very well. Opportunity already had gotten stuck for many days on a slope not even a fraction at the angle of this crater wall. They eventually had to completely alter the course of Opportunity altogether to maneuver around that small depression.

If it goes in it's pretty much stuck. It's a large enough crater it probably would be worth it, since winter is coming along and who knows if either machine will survive that.

However I believe that since both machines have already accomplished every goal set for them, that they should push the envelope and explore the region, not just a part of it.

Spirit is some 3.25 km away from where it began, and is nearing a large hill to explore, that is good. I'm not sure what near-by regions there are to Opportunity but I think that risking possible continued use for a possible success in a crater is folly. If nothing is found, that machine is ruined so to speak.

Where as if you maintain the rover's ability to navigate, it has the possibility of working for years...so long as the electronics do not freeze over during winter.

And you never know, a peice of anorthosite might be just over the next small hill. They've taken great photos of the crater, and it doesn't seem that there is good enough odds they'd find anything remarkable there compared to what they can find under a rock somewhere else. The bedrock exposed in this crater will not be much different from that in the one it began at.

I still wouldn't bet against it coming out, the problem in Eagle crater was slipping in the loose dirt on the crate walls. In Endurance it looks like there are some sections where the rover can traverse out via the rock sides. Which removes most of the slippage problems. The rocks being rough enough to get a good grip with the solid wheels.

As far as nearby sites of interest, I too am not sure how far away the nearest features (apart from craters) are. Opportunity could make better time than spirit due to the much easier terrain. The appeal of Endurance is that it gives access to deeper layers of bedrock. Allowing a better look into the past of Meridiani. Depending on how well the rovers handle winter, it would also be nice to find some similar craters some distance away to learn more about the size of the body of water that was evident in Eagle crater.