I use 99% IPA and have news for you: it’s only marginally better at best. The big benefit of 99% IPA versus store-bought 70% is that the remaining 30% (supposedly water) is usually not contaminant-free, which becomes evident when cleaning optical glass surfaces. For the best clean, I use an ultrasonic cleaner with 99% IPA for cleaning my circuit boards, something that is prohibitively expensive in the industrial sector.
Just in case the link expires, Here’s a screen grab.
To see this “dirty contaminant” phenomenon for yourself, take any dirty window or glass plate and hold it up to the light. Clean it with IPA, and you’ll likely find that you’re just moving dirt around, especially oils. This applies to any cleaning process. As a college window washer, I learned the importance of using a squeegee to push loosened particles aside, avoiding obvious streaks. This lesson was reinforced during my college days when I built optical scopes and again later in the semiconductor industry cleaning wafers. The point is, whatever solvent you use, wiping will only go so far, especially with persistent contaminants like oils from your skin. Flooding away contaminants is essential.
BTW: CSI’s rely upon this phenomena when collecting trace elements from a crime scene. 