I have married both and really don’t think you can go wrong. Elliot is definitely more mature and romantic, especially his 14 heart event. He doesn’t socialize much outside of your marriage (all spouses leave to head into town but he doesn’t really hang out with his friends). This bothered me a little, but overall 10/10 would marry again.
Sam is one of my favorites. He makes me feel like a teenager again. He is generally cheerful and relaxed. I really like his 14 heart event and how it hints at a career path for him. Sam still hangs out with his family and his friends which I like- I don’t want to be anyone’s everything. He can be a little lazy at times but he clearly adores you. 10/10 would marry again.
Edit: What farm map are you playing on? I sometimes let my farm layout determine my spouse.