If you are buying a major brand German knife made in Germany (not one of the stamped models from other parts of the world), the quality is consistent. They all use similar blade steels and construction techniques. The one exception is the larger Henckels kitchen knives which use Cintered metal technology (I think of it as welding different steels together).
What you want to consider is how YOU use the knife. Do you cut in a rocking motion or, do you cut in a cleaving action (vertical chop)? Does the handle fit your hand? Are the non-cutting edges rounded and smooth so you won't cut your fingers in use or get a blister or callous on your hand? I find the Henckels chef's knives to be better for a cleaving cut since they do not have the curve other German patterns do. For the grip, I find the Wustoff Grand Prix handles to be the best for my hands.
As my experience with the cooking knife has increased, I have found that I like the Japanese pattern much better. The light weight is less fatiguing during extend use. The acute edge geometry makes them "sharper" with the same edge preparation (final edge sharpening or polishing). These knives will not tolerate abusive use as well as traditional German blades (meaning don't cut against a ceramic plate, don't cut frozen food, don't cut against bones).
My personal favorite at the moment is this model:
It is a handmade knife from
Shinichi Watanabe from Japan. The blade is made from Carbon steel so, it takes a little more care to keep it from rusting but, I find the extra trouble to be minimal and worth the effort. I should note that the Santoku style is also available in a stainless steel version from other Japanese makers as well. The German Santoku is a thicker blade and does not cut as well.
The Forschner/Victorinox line is a good value priced choice. The steel is a little softer then the German Wustoff and Henckel models which makes it easier to sharpen but, it dulls faster and will not work as well on frozen food (for example frozen bell peppers that are being sliced for a stir fry dish). At about $20 to $25USD for most models, they are a bargain. Personally, I like the extra wide 9inch model in the Fibrox handle best. The Fibrox handle won't swell or crack when left in the bottom of the sink for a long time. The "wide" blade self aligns when you cut thick items like large potatoes; this help you make straight cuts since the blade will not "twist" in your hand as you cut. With the wide chef's knife or the santoku, it is easy to dice vegetables and then lay the blade flat against the cutting board to scoop up the food and put it in the pot or dish.
You may want to consider purchasing your knife in the mail from a different country to avoid high taxes and other local market influences that increase the cost of the knife. Knives in particular seem to be more expensive in Europe then other countries. Buying the same brand knife and the same model in one country versus another can have a large price difference that makes the shipping cost insignificant. In my own personal case, I have had good success buying kitchen knives out of the Europe since I do not pay the VAT (Value Added Tax). Japanese handmades are another bargain for me. Knives coming out of Japan (this biggest issue the language barrier) ship very fast and cheaply (I use Japanese EMS which is 2 days from Japan to my home in Arizona USA for a cost of $8 typically).
Finally, you might want to consider visiting this forum
Knifeforums - kitchen knife forum. That forum is specific to kitchen knives and has a lot of very specific kitchen knife information in it.