Ometepe or Jinotega? Can only do one or the other in the time we have!

I would say definitely Ometepe but take a taxi to St Jorge from the border and take the ferry from there. The only thing that I question is time. When are you coming. If it isn't for several months, Ometepe is the place. If you are coming now you may want to go to Jinotega. The reason being the amount of seismic activity that is happening is Nicaragua and not being mentioned in the states. LOTS of earthquakes around the country, pretty big ones. Parts of the country, including Mangaua are under red alert. Ometepe is an active volcano, not good right now. North would be safer.

Ometepe was quite tedious to get around and many of the sights were underwhelming. (waterfall, bathing springs, beach itself etc)
That said I had some good lake fish dinners there and met some nice people and the three nights passed nicely. The tours and treks filled the days in. Get a dorm in one of the fincas and you can live cheap and hang about for weeks, if that's your thing.
Yes you can hire a motorbike but then the dollars start racking up. I hiked Concepcion and have just posted about it.
It was nice for the open air and rural feel but I also wasn't that amazed by the place.
The port town was OK and I can see a case for staying there but then again the point of the place seemed to be the beach and lake.

Oh wow, I just looked up the seismic history and yeah there has been quite a bit of action going on. I don't even know what to say! I have never really experienced an earthquake. Are you down there right now? Thanks for the info!

Also, thanks to all who replied. I really appreciate your insight!

I am on the Caribbean side so I get none of that. We just get the news and updates from the embassy. Managua has been very active. Nothing in the last week or so but before that it was almost every day. There were also some to the west of Managua. Like I said, the embassy said Managua area is dangerous at this time. I myself would think twice about planting my butt on an island with an active volcano until further notice.