I've been a ski instructor for 11 years now, and have achieved my PSIA Level III (ISIA) cert, and should be completing PSIA-E's Freestyle Accredidation this summer (water ramps). From my perspective, I didn't want to patrol. They need more certifications (first aid, cpr, and others) and many areas only pay a small percentage of their patrolers (the rest get free skiing for them and their family, but not parents or siblings), but the perks are a little better. I'm pretty sure people associated with NSP (National Ski Patrol) get comped where ever they ski, however, they have to be on duty, even at other areas.
For me intructing is just fun. I won't lie, there is not a lot of money to be made doing it, but you get to ski a lot. Pretty much all areas should offer "clinics", which will allow you (as a new or returning instructor) to improve your teaching, versatility and your personal skiing. However, keep in mind that there is a LOT of politics in the Ski Industry, and many ski schools are like an "old boys" club. It can be difficult to break through the new instructor/good instructor mental barrier that many SSD's (Ski School Director) will have.
When I started, new instructors taught beginers, almost exclusively. However, much of that mentality has/is begining to change. A lot of new instructors are teaching a lot of lower/upper intermediates now. The theory is that the "better" instructors take the beginers, get em going, get em hooked on skiing and once they know skiing is now in their blood, they pass off the students to other instructors. Now, the problem is that many ski schools are VERY slow to adapt. New ideas, new tecniques, new pursuits are typically things you have to pursue on your own (such as newschool). However there are some very good newschool programs as well, just depends where you are.
The way I continue to look at being a ski instructor is this. The money tends to suck. The connections are great. The people are great (even the shitty customers you occasionally deal with end up providing a laugh in the bar). The skiing is great. By being an instructor, I've averaged about 100+ days a year for the past 15 years (season pass before I taught) - that's more skiing than most people do in a lifetime and I'm only 26. Working with the people that I have, I have been able to make great strides in my personal skiing, my teaching, and my knowledge, as well as pushing my own ideas, and pursuing my own passions (freeskiing/newschool). Could I have made more money, yeah, but in the long run, to me its been worth it.
life is too short to have any regrets