Do German or Japanese knives hold their edge longer?

The reason you're seeing conflicting opinions is because there are a number of factors (including steel composition, grind angle, grind profile, and usage) that contribute to a knife's edge-holding ability.

German/European knives are made of a softer steel than Japenese knives - they need sharpening more often but are easier to sharpen because of the softness. Since the steel in Japanese harder, it needs to be sharpened less often.

The other factor is the angle of the edge - the German/European angle is flatter than the Japanese knives. This means the German knives take 'abuse' better on the edge and requires less sharpening because of that. You can see below that there are two different angles:

As far as which requires sharpening less, I'd say it depends on how general purpose your knife is going to be. If its going to be going through bone and all sorts of things, the German edge will probably stay a bit better and the softer steel will re-hone better. If you're mainly cutting veggies, breads, cheeses, and other soft items - the Japanese knife will last longer because the difference of edge doesn't matter as much as the steel here.

Yes, Japanese knives are made with harder steel so they will hold an edge longer. On the other side of the coin, they may require a more expensive honing steel (global ceramic for instance) and may be harder to sharpen when necessary. For the sake of conversation, Zwilling, Wusthof, Shun and Global all make superior quality knives. How do you decide than? Think shoes. Which ones feel the most comfortable? Look at the shape of the blade of the chef knife. The Zwilling has a more severs arc towards the tip of the blade, facilitating a rocking motion. Ask you retailer if you can cut some veggies and se for yourself which fits your cutting style. Any knife in this class should last you a lifetime. Take the time to get it right.

If you're not that comfortable with sharpening tools, I recommend that you stick to stainless steel knives and stay away from carbon steel. Henkels, Wusthof, Sabatier, Victrinox, Shun, etc., are going to be about equivalent here. Regardless of what country in which the company is headquartered, most of these knives are actually made in China.

Global knives are special; I strongly recommend that you not consider buying them based on sharpening alone. Their steel handles, flexibility and razor sharpness are not for everyone. Make sure you try them and like them first. Global knives will, indeed, require less frequent steeling or sharpening.

Most other Japanese knives are carbon steel and single-sided, and require special care. Again, not recommended for someone not interested in home sharpening.

If you get a good sharpening steel (Global knives will require a ceramic rod), and "steel" your knives ever other use or so, you won't need to have them sharpened more than once every couple of years unless you're doing a lot of chopping bones. This assumes that you're using a sensible cutting board (wood or soft plastic). So taking them out for sharpening once every couple years isn't a big deal.

When you do take your knives out for sharpening, make sure you get someone who knows what they're doing. A lot of knife-sharpening places use low-grit belt grinders or stone wheels which take far too much steel off the knife and ruin them. I certainly wouldn't buy knives which are too expensive if you're going to let someone else sharpen them.

Japanese knives come in quite a spectrum of steels and tempers nowadays. I'll differentiate by hardness range

56-59 HRC types: Made from relatively soft conventional stainless, usually in a monosteel construction. These are a direct improvement of the stainless knife as we know it in the west, albeit slightly less abuse proof and geared more towards performance when used correctly. Maintenance regimes known for western knives can still be applied to some degree - rarely sharpening but rehoning often with eg aforementioned ceramic rods (some types might even still be compatible honing steels). More edge retention than even softer ones. "old school" western types can be expected - but nowadays, even some German makers make knives that fit this category.

60-64HRC types: Carbon steel, very high grade conventional stainless (like VG10, Gin-3) and so called PM steels (like SG-2) are used here, often in a laminated construction (awase or so called-damascus that is usually still an awase design). Maintenance regime differs. Honing will be done via stropping (on paper, leather, softwood...), never with honing steel, and using ceramic rods is also not well advised here (they are slightly abrasive and can leave a rougher polish on the edge than it had before, and they can create too much punctual stress). So the escalation from stropping will involve an actual fine whetstone, which you might need more often than a "full" sharpening on a western knife. Full sharpening intervals will be longer, though, and the level of sharpness a knife can be kept at for use is quite higher with that type. These knives will not be very abuse proof, but use with board impact, eg chopping, unless done clumsily or with heavy force, is not abuse, that is what these are designed for more than western knives. Actually, using western technique (especially using walking-rocking techniques while applying significant pressure) can be worse for these.

65HRC+: Carbon or PM steel, practically always in laminated OR differentially tempered construction. Edge retention is very dependent on the cutting surface and technique used (either the edge or the board absorbs the damage, there is no more getting out of the way), as well as what "configuration" is chosen during sharpening (microbevels, angles... you need to be MORE conservative than with the category above!) - and can be extremely good or surprisingly poor. Stropping will still work but be somewhat less effective, so maintenance relies on the fine stone even more. (From my experience, with the laminated type - this likely does not apply 1:1 to differentially tempered!), if used right, these can maintain a "very decent" sharpness for an extended time, but if you want "scary sharp as fork for a reasonable time" you are better off with the 60-64HRC group. These are knives that break before they bend, so abuse can be catastrophic.

I have found that my cheapo Japanese knives, bought from local Florida Asian markets stay shaper longer and are in fact much sharper than my really expensive Henckel and Wusthof knives. I cook old school and rely a lot on my cutlery. I have also noticed that Wusthof wants to twist to the side when cutting coarse meat. I am assuming that it's all about better steel in the Asian knives.