I actually own both (the only two red dots I own).
The Holosun "HS403A 2014" pros:
- A more focused/fine 2 moa dot
- Auto-on by movement feature (a good "flick" to the side with your rifle will turn the dot on, a great feature)
- Auto off after 8 hours (never tested)
- 50,000 hours battery life (quite a claim and obviously never tested)
- Brightness lock (hold down the + button for 3 seconds at desired setting, dot flashes 7 times and stays locked at the current setting even if buttons are pushed until cycled off/on. Will also auto-on back to that setting.)
- Two mounts: low and high
- Low profile as compared to other red dots (no large dial on top or side)
The negatives:
- Crazy glare when a light source is behind you. The dot is still very visible but a red reflection really distracts the eye. I also experienced the same effect on the Bushnell trs-25 but not as severe.
- Battery compartment is on the bottom so sight must be removed for battery change out
- Must use blue lock-tite to maintain tightness of the mount to sight body. The mount will loosen after a few hundred rounds or a major temperature change. Also, the Allen head screws are only accessible from under the mount when using the low mount.
-The biggest issue I have is when shooting with two eyes open. The sights center of horizon is noticeably shifted to that of your other eye. Makes quick target acquisition more difficult. With practice it is manageable but annoying none the less. I have researched this issue and found that it has reportedly been corrected in later models. I apparently received an earlier model. I also did NOT purchase the Holosun red dot via CanAm but through the USA via a big box retailer so warranty return is just too much of a hassle for me. A picture of the misalignment/distortion I found:
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Overall I would purchase the Holosun Red dot again. As compared to my Bushnell TRS-25 I like it better in every way except for the horizontal alignment issue. The Bushnell does have a very slight alignment shift but its very very minimal.