This is a short note reflecting my experiences in these two countries.
While I visited Trinidad and other ruins in Paraguay, I haven’t actually experienced the country. I intend to go back someday.
When the catholic missionaries came to South America, they formed an experiment (strictly guided by the bible ofcourse) with the local tribes and the missions were formed in the region around Paraguay, Argentina and maybe Brazil. Apparently, this experiment was a success with peace between the church and the locals. I went to get a sense of these missions, first by heading to San Ignacio in Argentina. From there I did a day trip to Paraguay. Trinidad, in Paraguay, is the main town for these missions. I would recommend going to San Ignacio and Trinidad for these missions.
Uruguay has a few sights and is a great place to visit for a few days. I went to Montevideo, by first taking a ferry from Buenos Aires and then a bus (which is included in the fare). Montevideo is a beautiful city with a stunning waterfront walk, nice beaches and a historic centre. I would recommend doing a free walking tour to get a sense of the city. The city is easy to walk and I spent a lot of time walking around the city. There are lot of eating options especially if you love meat and empanadas. Uruguay has a lot of beautiful beaches lining up the coast. I did a day trip to Punta del Este to see the famous hand sculpture. I am not a beach person so I didnt go to any other beach. Colonia is a small town with the remnants of colonial architecture. I spent 2 days here and while it is beautiful, there isnt much to do here. I would recommend a day here and maybe 2 to 3 days in Montevideo.