There are not a lot of similarities between Macklemore and Bob Marley, but here are a few ;
Music - Both Bob Marley and Macklemore are very passionate about what they do. They both love music and its ways of speaking to people. They both used/use it to talk to people and send them a message. I think this is pretty much their only similarity. They both love/loved what they are doing/ what they did. Music is their life/was their life and will always be their life. Their body doesn't run with blood, it runs with music. Same with any other musician.
Inspiration - Macklemore and Bob Marley are both very inspirational people. Some may not agree with me, but this is coming from me. I think that some of Macklemore's messages are very strong ! Same with Bob Marley.
Differences
There are many differences between Macklemore and Bob Marley, here are some;
Style - These artists have very different styles, Macklemore's style is more Pop/Rap/HipHop/R&B while Bob Marley's style is more Reggae/Jamaican
Messages - Bob Marley broke cultural and racial boundaries to spread his message of love and positivity to the world, while Macklemore has many sides, he has a fun side, a serious side, and a strong side to his songs.
Style - Macklemore has a VERY unique style ! He wears what ever he wants and isn't afraid to be different. His style is very unique. From what I've seen in pictures and videos it looks like Bob Marley just wore jeans and different types of tops.
There is also the obvious similarities and differences like they are both musicians , or they lived different times, but I do not think that those are important nor necessary.