I have a Sora Shimano hand brake with shifter integrated. However, when I compare to the Shimano 105, I found the 105 is a lot easier to pull with my fingers. It is a lot snappy and smooth on the hand brake. I doubt there is anything to do with the brake calipers. Again, my Sora brake is like greases stuck inside the joint but I brought the bike brand new and I lubricated the joint with Tri-flow recently. Unfortunately, no improvement at all after lubrication. My Sora hand brake require more force to pull and it is a bit slow. A cheap MTB hand brake is even a lot better than the Sora hand brake.

Should I upgrade it? Don't judge me wrong, I am not rich. When it comes down to safety, the money I spend today could be well spend than tomorrow.

either ya need to work on hand strength or something's wrong, either the position or mechanics. Talk to the LBS cuz you shouldn't have trouble braking. If you have small hands, I've heard campy is better for that, so don't buy 105 if that's the issue.

I rode Sora for a year,upgraded to ultegra recently and ultegra braking isn't better... cuz I found nothing wrong with sora.

I notice a difference between sora and Ultegra(similar to 105 undoubtedly) in terms of the responsiveness of the lever, and the force I can apply. However, I don't see it significantly enough that upgrading would justify the price. If you have a shorter reach than most, Sora is actually Shimano’s only system that allows you to adjust the reach of the levers (not sure if dura ace and 05’ ultegra do, but their levers seem to be positioned better than their older counterparts). You may also want to try different brake pads as well.

Isn't that adjustable? My brakes were really tight and hard to use, so during a second tuneup, my LBS just loosened them up - much better! There was an adjustment under the brake hoods and it took him 30 seconds to fix.