Phormula-1
How I use it: After workouts, paired with Ignition.
I think of Phormula-1 as my post-workout protein option. When I finish lifting, this is the protein I reach for because it fits naturally into my recovery routine.
Level-1
How I use it: When it is tough to get a full meal in.
Level-1 fits differently in my day. I use it more as a convenient protein option when life is busy and getting a complete meal in is difficult.
Which one would I choose?
After a workout: I personally choose Phormula-1, usually with Ignition.
When I need something convenient between meals: I use Level-1.
I do not really view them as replacements for each other. They fill different spots in my routine.
Quick answer
If you're shopping because you want a protein specifically for your post-workout routine, start by looking at Phormula-1. If you're looking for an easier way to get protein in during a busy day, Level-1 is the one I'd look at first.