I used levels, though largely because I could pair it with a glucose monitor and not just see macros but also how it impacted blood glucose.
It was an interesting exercise for 6 months or so but in the end my conclusion was if I eat pretty much nothing but meat and veggies my macros work out fine and blood glucose looks great. If I eat much of anything else it does not. After a fairly short time in was not about learning anymore and more just an accountability thing, decided it was more cost than I wanted to pay for just accountability so I wrapped up the whole exercise.