A good question. By 'Using sheet music as a guide', I suppose you mean sight-reading. That's the technical term. In my opinion, sight reading is one of the skills that differentiates the men from the boys, and in my opinion, to learn to sight read really easily, is harder than learning anything else.
I really try to avoid memorizing any pieces, because for me every time I practice is an opportunity to sight read, and I try not to lose it. Except in the most advanced pieces where there's a lot of speed involved and all the position shifting makes sightreading very difficult.
A couple of years ago when I started on CG , I was very disappointed about my sight reading skills. I knew a lot of theory and I used music reading only for learning pieces, not for sight reading ( two very different things) but because of the bad sight reading I felt like a schmuck, so I worked on it quite a bit, and now I am where I wanted to be. It's probably the hardest thing I have done in music so I am quite proud of having developed this skill.
I prefer sight reading to memorizing, but sometimes I have no choice. Memory can fail you, easily, and the more advanced is the piece, the more easily will memory fail you, for example contrapuntal pieces are harder to memorize than homophonic pieces. Sight reading skills cannot fail you, unless the piece is very fast and there's lots of position shifts. Even then, you'll be surprised how much sight reading you can do even when your LH is going all over the fretboard at fast tempos. If it gets too difficult and I have to keep my eyes on the fretboard, I will momentarily look away from the score. In the score I will have marked a sign before hand, with a highlighter. That way I can return to sight reading as soon as the troublesome passage has ended.
The downside of sight-reading is that if you lose your focus, you can lose your place in the score, and as you don't have the piece memorized, you can mess the whole thing up. As long as you don't lose focus, if you can sight read well, you are pretty much unstoppable.
The other downside: learning to memorize won't take work, we are already born with that skill. Learning to sight read well will need special processes and and hefty amount of work, and the weaker the sight reading, the more work it will need.
Then again, it all depends on where you are and where you are going. Developing excellent sight reading skills is for the serious player and not the faint of heart.
I prefer to use the word 'serious' to 'professional', as too many people seem to believe that if one isn't earning money with music, isn't a professional.
For that matter, Bach never made a cent from his music. But I would not say he wasn't a pro