I'm Chinese-American, so you can draw your own conclusions from that haha. As long as you're a native english speaker from a country that has K-12 english education (quebec for example doesn't count because the national language is french), you shouldn't have too much of a problem. I'd say it hurts you more for NOT applying to all of em.
The ALT companies are all going to have some degree of shadiness to them. If you're American, you can probably relate to exploited foreign labor. In this case, you're the foreigner being exploited. For example, for you to draw full time benefits, you must work over 30 hours a week, so the companies will make sure that you're not scheduled for more than 29.5 hours per week, and they only count the time you're in the classroom as "working" time so they don't have to provide you with benefits like national health care, pension, etc. However, despite only being "paid" for 29.5 hours, you're typically not allowed to leave the school grounds during your work hours. During summer/winter/spring you're going to get a reduced (or zero) salary during those months since you're on "vacation" and some companies will pay you a daily rate for april/may since you're not working the full month. As long as you manage your finances properly, you'll be fine, but it can involve you paying closer attention to your money and planning for those reduced pay months.
Really, its not so much companies you have to look out for, but more the contract you get with the city you're placed in, and I'd make sure they provide you the details before you get on the plane. Like for example, RCS pays hourly in certain cities, meaning if you don't have class, you don't get paid. You'll get like 50-100kY in the month of July and zero in the month of August because of summer vacation. Interac is typically better because they're a big company, but because they're the biggest, they were the biggest target for activist groups. Some cities under Interac have full time benefits and the sort because the ALT's, in conjunction with the teachers in the city fought for ALT rights. But, they're also the biggest, which is going to make you a replaceable asset to them. Personally, I'd say within the big 3, RCS, Interac and Heart before branching out to some of the other companies. My last company was called Educational Network, and they by far had the best benefits/pay, very small client base of fairly wealthy private schools, and the company not only does ALT stuff, they work as a recruiting company for direct hire positions at said schools. Great company, but they only hire "experienced" ALTs. Meaning, you have to already have your visa before they'll hire you. That's a case where you're hopping between companies in between yearly contracts. That's the other thing, these companies only give 1 year contracts and they are VERY slow at giving them out. Meaning it'll be the beginning of March and you're still not sure if you have a job in April. As a survival technique, you need to be applying to ALT companies in February to make sure you have a job. Keep on the ball and you'll be fine, realize that the companies are likely not going to show you any loyalty or longevity, there's no reason for you to do the same. I used to work in Urayasu at a school I loved, but my company lost the contract to a cheaper company, and the new company had REALLY bad contract terms. We didn't find out until February and I was left scrambling to find another job. Since then, if I don't know where I'm working the next year with 100% certainty, I'm looking for a job starting in January/February.
Personally, I enjoyed working as an ALT quite a bit, but I've been very fortunate with my schools and my coordinators at the company. Currently, I'm actually a full time high school teacher at a private school and no longer work for a dispatch company. It was a long path to get here, and involved a lot of overtime. My biggest suggestion to you if you're actually serious about pursuing a career as a teacher is to learn the language and culture; live it and breathe it as much as you can. The more fluent you become in Japanese (refer to the thread about "how fluent is fluent" for my opinion on that), the more doors that are going to open for you. When I first got here, I avoided talking to non-japanese like the plague. My social circle was 99% Japanese, and no one spoke English. Trial by fire and I survived it to get to a fairly fluent level. JLPT is pretty meaningless in the professional world aside from being a resume buffer. I likely couldn't pass the JLPT N2 without studying a crapload, but I function better in Japan than most of the N1 holders. Second, make sure you put a ton of effort into your lessons, because people notice and they talk. Word of mouth is the best advertisement here, and can open a number of other benefits for you. A principal at a previous school I worked at cosigned my apartment for me, wrote me letters of recommendations that opened even more doors for me, etc. Our good relationship began because I recognized his Japanese dialect that most of the local teachers didn't even recognize.
One of the most common mistakes most english speakers make...
Intents and Purposes, not Intensive purposes =P
