I actually get this question a lot. The knives are very similar with regard to geometry and profile. Likewise the fit and finish on both is superb. The steel, however makes the difference. Figuring out which is the best fit for you depends a lot on your personal preferences.
First, the Suisin... When i first started using these knives, i didnt really understand the steel. It was only after i spent a significant amount of time at Suisin, sharpening a ton of knives, training with their craftsmen, talking to them about sharpening, and testing out their knives did i really get what makes this knife great. With the steel (19c27), the heat treatment, and the proper sharpening, this knife takes a great edge, has awesome toughness, and is easy to maintain. For me, learning the sharpening was key. This steel and heat treatment responds well to having a thin edge with a high angle microbevel (around 40-45 degrees). I only put the microbevel on one side (usually the right side because i am right handed). With this kind of sharpening, i get much more out of this knife. The toughness is greatly increased, making it a knife i dont feel like i have to baby. Fixing it is easy and the knife can be sharpened in just a couple of minutes on a high grit stone (6k+). I also happen to like the handles on this knife a lot... they are just the perfect size and shape for me.
For me, this new sharpening has made this knife stand out again from the many similar knives out there... including the tadatsuna. No other knife like this that i have tried responds quite the same way to this kind of sharpening.
Now, the Konosuke HD. I also really love this knife. What makes it special is that is sharpens as quickly and easily as carbon steel and takes a better edge than most stainless steel knives that i have ever tried (much closer to carbon than stainless). It also has increased toughness when compared to carbon equivalents (such as the white #2). I like to think of it as a stainless carbon blade. It pretty much takes the best of carbon and blends it with the best of stainless.
The Konosuke takes a better edge than the suisin, but the suisin holds an edge longer and has better toughness. The Konosuke is easier to sharpen, but touching up the Suisin is quicker. Picking which one is right for you is mostly just a matter of personal preference. They are both great knives.
Hope this helps.