This is actually both a really easy, and a really difficult question to answer.
One of the wonderful things about art is that it is different to everyone. So you need to think about where you want to get to. Is it photorealism? Is it accuracy in still life? Is it shading? Some artists want their portraits to remain abstract, some want pinpoint accuracy. From your two pictures you'd need to let us know how much you like each one. I can see arguments for either being the better one - so trying to do that here would be a bit opinion-based.
So identifying where you want to go is key - and a really useful way to do this is to look at art. In galleries, in books, online, everywhere.
Then practice. Either with tuition, or help from sites such as this, or from the plethora of YouTube videos teaching this subject to guide you. And show people if you do need their opinion. Ask them what they like - but remember you don't need to follow their preferences.
If you really want to progress as effectively as possible, there isn't really a substitute for art classes, teaching technique, styles, history etc.