why would this trip not be for the faint of heart? there are lots of tourists that take these trips.
Both of which are decently traveled. Neither are top tourist destinations in the country, but neither are particularly remote in that you are one of the few to do it. If you are looking for more remote, and something that very very few people do, i would recommend heading north and try out the Rio Coco along the Honduras border. Waspam, Asang, and over to the Puerto Cabezas area. Now thats a trip not for the faint of heart.
But as for your 2 suggestions, the Bluefields / Pearl Lagoon trip has more people, but not necessarily more tourists, its just got bigger cities and more people traveling back and forth. Most tourists choose to fly. You only have 10 days, so the Corn Islands trip is going to be a bit more hurried. If you are going by boat, It will be 2 partial days of travel each way all the way out to corn islands and back from Managua, and since most everywhere along the coast is only reachable by boat, you will only be able to fit 2 or maybe 3 coast destinations in most likely, depending on the travel and the timing of everything.
If you do spend some time out there, i recommend checking out Kukra Hill, Monkey Point, Set Net.
Very few tourists make it farther out than the bluefields/pearl lagoon/corn islands triangle. And partially for good reason, since there isnt much of anything out there except small isolated villages and a muddy coast. Thats not to say its not worth going, but it depends on what you are looking to do on your trip.
The San Carlos area is more frequented by tourists, but pretty much in a straight line. San Carlos, down to El Castillo. Most dont go much further, some go to Greytown, and then back up the river. Lots of hanging out on a boat. Lots of jungle scenery after jungle scenery after more jungle scenery. There is more history and good blog scenery to take pictures of and post for your friends. Once you hit the Indio-Maiz...you will feel remote for sure. I have yet to do the solentiname islands, so i cant comment first hand on them. But once again, with only 10 days, a lot of boat travel, and the limited departures could eat up a lot of your time. I doubt you would be able to make it to greytown, check out the indio maiz AND do solentiname islands, unless you flew to/from san carlos, and got the timing down right and hurried through everything.
There are more options for hostels and basically tourism in general in the san carlos/rio san juan area. You can stay budget dorm room style for cheap, or camp. Or there are expensive eco-whatever buzz word resorts too. its not difficult tofind a place to stay once you are there.
The carribean coast has much less of that, and outside the pearl lagoon/bluefields area there is little to nothing set up for tourists. Though if you are a nice guy and into getting to know the locals, getting a place to sleep and a meal shouldnt be too difficult. you might need to stay in bluefields, and just do day trips to some of the nearby areas.
as for comparison....it goes without saying the carribean trip will have different feel than san carlos / solentiname islands. The people are different, the language is different, the food is different, etc. The carribean part is like a completely different country.
