Im an INTP, Ive known a good ENTP friend for many years and in the short term the differences between us are minor.
A simple way to describe the difference would be that INTP is more stable and puts more thought into our actions. ENTP more impulsive and puts more effort into maintaining a social life.
Depending on our focus in the short term we can both seem similar. Im a more socially capable INTP, Ive known a lot of different people in my life so when I need to be capable socially I can actually be an effective leader of a social group. Long term though I will get bored of this and push people away so that I can do my own things.
An ENTP is less likely to do this and will put a lot more effort into maintaining a social life, theyre also more prone to just bounce off to do something new.
Id say im more serious and care more about logic and accuracy, ENTP care about these things too but theyll be more laid back for the sake of being social where as an INTP is more likely to just not give a fuck what you think.
Take a look at the differences between the INTP and ENTP subreddits for example. The ENTP reddit has the occasional serious discussion filled with more jokes, the INTP reddit has more serious discussion and occasional jokes.
Basically its a large spectrum, even within the individual types there are large differences in personality.