I like how in the second one most areas are either mostly dark tones or mostly light tones, except for around the eyes where there’s a much wider range of values. Really makes them pop

Well i can try to help. Ill say things coming from my own journey. So first, the second one is much better. These look very quickly done, if you are working from photo references i would recommend spending a lot of time with planning and measuring. When beginning, it can help to really measure the photo and transfer it to your paper so you get a feeling for the relative sizes of parts of the head. Your own mind isnt allways truthfull and eyes and so on can feel bigger or smaller than they really are. For example the eyes and chin of the second portrait. Second thing that i think is somewhat lacking is the structure or three dimensionality of the portrait. Studying a plane head or some prokos head drawing tutorials can help you undestand the planes of the lips, nose and browridge better. What i would recommend is first, draw from a photo a realistic, very measured portrait copy. It should help you later when you study plane heads, or some other structural methods, to better form the model of a head in your own mind. The pencil choice i would use would be a harder pencil, an HB for example. Start with very light marks for the lines, when rendering giving it a light later of graphite and going darker every layer. And be very patient 😁