What would be the best fingering for the left hand here? I was trying something like 4 3 2 1 ... but the cross with 4 and then a 3 afterwards is a little awkward.
I would personally stick with 4-3-2-1 in the left hand, and then 1-2-3-4 in the right, because it feels a bit easier to me to have both hands crossover at the same time (every four notes). However, I do have relatively big hands.
The other option I see for the left hand is 2-1-4-3; I’m not sure if that makes things easier for you. You could even do 3-1-3-1 but that seems a lot harder since you’d have to crossover twice as often, and it doesn’t really “fit” in terms of phrasing since we have a pattern of four notes, not something like two notes-two notes.
If you're going with 2-1-4-3 in the left, and want to crossover at the same time with your right, you could do 4-1-2-3 with your right (and perhaps 2-1-2-3 for the first arpeggio). Actually, upon trying this, I am able to play it more naturally and quicker than the 4-3-2-1 fingering in the left, at least upon the first few trials.
Edit: sorry, for some reason while writing the last paragraph I thought the right hand started on an E-flat. Since it starts on an F, I'd just go with 1-2-3-4, and I don't really see another convenient possibility for the right hand. Maybe 3-4-1-2 (and perhaps 1-2-1-2 for the first arpeggio), but I am finding 1-2-3-4 easier.
With the caveat that fingerings are personal depending on the shape of your hand, its size, and your own dexterity, 5-3-2-1 is what works for me by far.
Now I can try to "justify" that choice too in that:
4-3 is generally not as strong as 5-3
beginning (or ending) an arpegio with the 4 instead of 5 is also believed not be as strong for most (obviously, it will depend on the specifics)
Note that you should also find something that works for both hands when played together. In my case, with 5-3-2-1, what works best on the right hand is 1-2-3-5 as well as opposed to 1-2-3-4.
Practice various fingerings by position, slowly first and then in tempo, and one will soon stand out as better for the longer term.