pros/cons? I'm thinking I will use the open like stock.

I use sealed bearings. They are lubricated for "life", no repacking the bearings. It is difficult for water or dirt to get in them. If they ever get loose, just replace them. Small price difference if any. I still grease the axle, seals and bearing spacer area when assembling. I keep the original or new seals in place.

Replace your brake shoes at the same time if they are old.

Ive popped the cover off sealed bearings and seen very little grease. Ive re-greased them and put the sealing cover back on.

limited use bike, gotta go sealed for the clean factor. Can put a little grease in there to keep the axle and seals lubed up.

sealed, something other than a Chinese make if you can

Just bought front and rear bearings local. Bearing house downtown Portland and all were in stock. Sealed Koyos which are still quality bearings. All 5 bearings and 2 seals for $74.
I'm confident they'll last as long as I do.
Popped the cover off each bearing and they all had grease, not packed, but enough. If you pop a cover and there's no grease visible, pop the opposite side off and you'll likely find it. I understand that sealed bearings have roughly a 25% pack per design.
Koyos are still made in Japan. They had others there that were China made for 1/3 the price.
And, I see no advantage for open bearings, once the contaminants get in, they won't purge themselves, so the key is to not let them in. Rub a little axle grease around the seal as you install them for a little added barrier.

The big advantage to open is it's a little easier to clean and repack... and they might drain better than the sealed bearings if you ran through a lot of over-the-axle water crossings where a little water might get into a bearing.

A fellow Enduro/ 2-day Qualifier rider put Zerk fitting in the steering head, got tired of messing with greasing the bearings.

There's a difference between shielded and sealed. Z / ZZ shielded one or both sides. RS / 2rs sealed one or both sides. A sealed bearing shouldn't alow water in unless it's shot and needs replacing anyway. Shield will alow water / dirt / and what ever in that will fit between the the small clearance between the shield and inner race.
A sealed bearing should not be packed full of grease. For the lubrication to work properly there needs to be air space. As Nutt said, by design I think 25% is probably correct.

I like sealed no reason at all to have an open bearing these days. I too ck lube quantity, re paked very few (when new)