This question has a lot of answers so I will list the pros and cons of each. Let’s start with Polyurethane or OMU pros.

Polyurethane Pros

1. Tried and tested, an industry standard for over 65 years.
2. Cost, most commercially available floor polyurethane is around $15-$20 a gallon
3. Has a thick build more solids than water based finishes
4. Has an amber tint also called “grain enhancing”

Polyurethane Cons

1. VOC’s the average floor grade polyurethane has about 550 g/l even new VOC compliant poly’s are at 450 g/l. “you should not be in the house”
2. Dry times depending on the current humidity and temperature I have seen polyurethane take 3 days to dry before another coat could be applied. Minimum of 12 hours
3. Color change over time to orange, I placed this in the cons due to the fact that color matching a repair to aged poly is extremely difficult and the repair will not change with the rest of the floor.
4. Can contain lead drying agents pre 1978

Water based Pros

1. Low VOC content typically around 225g/l-150g/l very light sent
2. Dry times dries to the touch in an hour fully cured in 3-10 days
3. Is harder than polyurethane
4. Multiple coats can be applied in one day
5. Has a true clear finish but can have an ambering sealer added to replicate grain enhancement of poly.
6. Much less color change then poly over time
7. No lead content at all

Water based Cons

1. Cost water based finish is 3-4 times more expensive then poly around $60-$120 a gallon
2. Less solids “thinner build” need at least 3 coats
3. Only been used commercially for 15ish years
4. Most contractors are resistant to change so not as commonly used in the industry and has a different skill set to apply.