2013 marked my first foray into the joys of international travel, doing it not once but twice. In an interesting twist of fate, both of those countries started with the letters "JA" (the only two in the world, even). They are worlds apart, however, both in physical distance and atmosphere/culture. Let's do a pros/cons.

Japan

Pros

• Everybody is very respectful of others and mostly keep to themselves. The introvert in me loves this.
• It's clean. Though some places may look a little run down, the overall level of cleanliness is pretty high
• Shit is organized. There were a couple of times when the road to Asakusa was blocked for utility work or something and they had cones marking precisely how traffic was now being directed... and also a friendly guy there to point you in the right direction.
• Conversion rate is essentially 1JPY = 0.01USD. Makes for easy conversions.

Cons

• Probably contrary to the cleanliness bit, there was a constant smell of old garbage/water mold lingering around. It was only in certain spots, but it was a trifle off putting.
• Cramped. The trains, the layout of the buildings, etc is designed to pack the most stuff into the smallest space. Not great for my introversion and large body.
• Language barrier. They really don't speak English well when they do at all.

Jamaica

Pros

• The resorts are such that you really never need to leave; all your whims are attended to
• The beach
• The exchange rate for the Jamaican dollar is about 1JMD = 0.01USD. Granted, you may as well just use American money because it's less likely to depreciate in value and everybody takes it anyways.

Cons

• It may seem like everybody is super friendly, but it's that kind of friend that stops paying attention to you when they find out you're not popular/don't have money/etc. Money gets you everywhere.
• The food will make you shit... a lot and explosively. If you're wise, you'll pull a Steven Spielberg and bring your own food.
• The Jamaicans running the tourist stuff are essentially parodies of the stereotype. So much "mon", Bob Marley, and general "no shits given" (the above shits excepting) were way, way overused. Also, my brand of "fun" and theirs are very different, but they'll try to force it on you anyways. Granted, I've had friends try to get me involved in such activities as well. Looking at you, dancing...
• Jamaica is a third world country. Outside the fancy resorts and tourist spots, it's really fucking run down and the people are super poor.

So, in the battle of J countries, Japan is the obvious victor (though, my opinion is certainly heavily biased).