What’s the difference between standard (freebase) nicotine and nicotine salt?
There are two major differences. First, standard nicotine has a stronger throat hit compared to salt. Standard nicotine also releases nicotine into the bloodstream at a more even rate than salt.
Salts are useful for those trying to quit smoking because you can vape higher strengths of nicotine without a harsh throat hit. The faster nicotine absorption of salts also mimics the effect of smoking more closely.
That said, some people prefer the stronger throat hit of standard nicotine, so which one you choose is really down to your own needs and the kit you are using. For instance, nic salt concentrations above 6mg are not really suited to sub ohm devices because the nicotine hit would be too great and the flavour too harsh. The best devices for nicotine salt strengths over 6mg are lower wattage (under 20W) with high ohm coils (around 1.2-1.5 ohm).