I have done this before for a huge site in 7 languages and had many a debate over the years with Matt Cutts on it.
The short answer is multiple TLD's
Reason:Matt Said in a video and for the life of me I am unable to find it. That if they allow sites to rank in every country then people will just create content for them to get extra traffic, if they created a tool in WMT people would just tick every country saying their site was relevant. The only sure way was if they created a TLD and put some hard work into it.
doing xyz.com/jp/ is an option and then targeting a "Geographic target" in "Site Settings" but it will not get the same power as a TLD specific to that Geographic location. TLD are a very strong indication of location.You will have to setup sub folders in WMT like separate sites and target each directory with the "Geographic target".
Also, this is something I have been saying all day long, separate sites are good because you never know when Google is going to slam you with a penalty for a silly reason. You would lose all your locations in one go if they are on the same domain. But only have one site down if it happened.
Also have a good read about "hreflang" this will help you make a few decisions as this is new since the time I worked on the Multi-regional site.