I agree. I had a partner many years ago and it was a disaster. Partnerships are a dangerous thing because businesses are so dynamic- meaning- they are always changing and evolving to meet the needs of growth. You will never see eye to eye with a partner when key decisions need to be made from time to time to adapt.
An investor is a completely different ball of wax. They are a partner with a vested interest in the business, but no real say for day to day operations. If you are going to have a "partnership", this is the way to go.