There are a ton of reasons why brightness may be different and the difference of 10% is barely noticeable to the human eye.

Power delivery could be more efficient, but it is more likely the quality of the optics or a different color wheel in use.

A larger/higher quality lens on a projector can allow a fair bit more light to pass through it making the same lamp, much brighter. Kind of like how a larger telescope lens makes the same star appear much brighter.

The color wheel is a huge factor in projectors. The lie of brightness, which almost all DLP manufacturers participate in, is the use of a 'clear' segment in their color wheel. It increases white brightness at the cost of color brightness. So, you end up with dingy colors when brightness is maximized, and a much dimmer image when the colors are properly calibrated.

This is why 6 segment color wheels (RGB/RGB) are often considered the best in home theater situations because you can get excellent colors in a good room and you may actually end up with more overall brightness because it has better colors at all brightness levels.

In the event my other response doesn't get get read, I'll repeat it here and add some more details:

Confirmed!!! I have just replaced the OSRAM P-VIP 240 / 0.8 E20.9N we recently purchased (a week ago) as a lamp replacement in my BenQ W1110 with a Starlight P-VIP 240 / 0.8 E20.9N purchased from PanPacSight and the difference is staggering. EXACT same part numbers! Unlike the OSRAM, the Starlight brightness and color saturation is a joy to view, where the OSRAM is dingy and green and frankly unwatchable. This newly purchased Starlight is the exact lamp I replaced the original lamp with 18 months ago. The previous Starlight mirror is peeling off the inside of the lamp. I do not recall that the just replaced Starlight lamp ever looking as nice as the Starlight lamp I just installed. Sadly, I think you need to purchase a from a few vendors and do some comparisons.

I didn't take photos to show the differences nor do I have a tool to officially measure the differences in color saturation and brightness. I can only assume the vendor I bought the OSRAM from is selling old/ used lamps. We bought 2 lamps and they are both being returned tomorrow. Those OSRAMs were purchased on Amazon...as were the Starlights.

So, identical part numbers with utterly different performance! I also have a 2200 lumen lamp incoming next week test against the Starlight.

Further, I made no other changes to re-assembly or any adjustments beyond ensuring the lamp housing was as carefully reassembled as possible.....as this W1110 housing is a flimsy thing. That said, there seems to be nothing wrong with my W1110 except the plastic getting a little beaten up from 2 deep cleans and about 6 tear-downs and rebuilds.