its the easiest third year course so dw too much, 3411 is an easy and great course and britz is a good lecturer. Should be fine as long as u can do basic row reduction with matrices and can do the modulo stuff from discrete
Similarly 2521 isnt too hard and is also known as the easiest second year course
So if u got space in timetable id pick both, if you need to choose id go with 3411