Man Shing and Wing Shing are possibly the most reputable in the list (at least they are mentioned the most often in CS), while it seems DC Fever and Tin Cheung could generally have the lowest prices. YMMV!
Note caveats such as whether the product are offical HK imports with international warranty or are grey market, and if the shop charges for credit card transactions (~2%). Man Shing and Wing Shing do not have CC surcharge. Generally avoid any shops that have giant neon signs for "Nikon", "Sony", "Panasonic" or whatever instead of a shop name.
Make sure you get a printed receipt (not handwritten) with the shop name in the letterhead. By law, you have 7 days to get a full refund if you are not satisfied. The printed receipt is also needed for the International Warranty to be honoured over here.