It isn’t a surprise that there are a lot of teams with circular logos in baseball. It make sense, a baseball is circular, and a circle is a shape that is aesthetically pleasing, so a lot of teams use it in their logos and patches. Over the last 5 years or so, a lot of teams as they have redeveloped their uniforms have included a new circular logo in the set. These new patches don’t include teams like the Mets, Cubs, or Yankees, who all have logos based on a baseball, so their primary logos are going to be on a circle. Rather a new crop of teams have started, or reinstated and joined other teams who take their primary logo and place a circle and border around it:
Baltimore (Home and Away)
DC (and another)
Pittsburgh (Although I don’t know when they wear this)
San Francisco
Toronto (Although not a patch, just their new primary logo)
Boston
Minnesota (Only used in 2010)
Oakland
Texas
Seattle
Los Angeles Angels
San Diego
In that above list, Baltimore, DC, Minnesota, Angels, Toronto and San Diego were definitely added within the last few seasons. If I had to guess, the circle with border feels older, retro, even if it isn’t and the majority of uniform changes we have seen in the last few seasons have been to make uniforms feel more like the older days. Some other trends include that currently, there are no teams in the AL Central that have a circular path while every team in the AL West do have one.