Saxon Math is an advanced math program where you are introduced to a new concept every day. The daily work load consists of a few problems related to the new concept and several problems reviewing concepts previously learned.
Pros and Cons
The greatest advantage of Saxon Math is that your child is continually reviewing concepts and thus becomes better at retaining them. This is a huge contrast to your typical math curriculum where they learn a concept for a month, move on and quickly forget what they learned last month.
The only drawback with Saxon Math occurs if your child suffers from any sensory disorder or struggles with math conceptually. In these situations the curriculum is too rigorous and becomes a frustration. (That being said, I taught Saxon for years with little to no problems.)
The Math-U-See program is a multi-sensory math approach. It is designed to teach math so that it can be applied in every day situations. Math-U-See is a systematic and accumulative approach that builds as your child progresses.
Pros and Cons
The greatest advantage of Math-U-See is that it's concepts are more easily applied to life and therefore much easier to grasp. The music and manipulatives are great for children who struggle focusing on school and learning math concepts. This curriculum is especially effective with children that have ADHD.
The drawback of Math-U-See is that you need to give placement tests to determine where your child needs to start as it is not broken down into grade levels. This is not a problem if you are going to school long-term, but quite difficult if you just want to homeschool for a year.
I know I am not an expert on these Math curriculums, but I hope that this information has been a little helpful.
My advice... If you want a conceptual approach that is amazing go with Saxon. If you want a fun approach that leans more towards whole learning go with Math-U-See.