We are back to the old arguement of pitch for speed or power for speed neither which is totally correct as it should be pitch for energy power for energy.
That argument is largely perpetuated by airline pilots who fly big airplanes that do require such thinking. In a half-million pound airplane, one doesn't have the operational flexibility that one has in a 172, when landing. Stable approaches are critical, and one is more rigidly locked into concepts such as power for speed and pitch for the glidepath. These debates end up trickling to a light airplane discussion, and it's not nearly so critical a subject (
it's also worth noting that while pitch and power are very interchangeable on a light airplane while conducting an approach, they're a lot more interchangeable in a big airplane, too; more so than most of the airline-types who create these arguments may realize. It's also worth remembering that a lot of those folks do far more of their approaches and landings through automation, so their view of what you should or shouldn't be doing in a light airplane may not necessarily be your best source when learning to land the 172).
If you're high on the glidepath, you may elect to reduce power, or you may elect to pitch down, or you may elect to reduce power and pitch down. You already know that decreasing your angle of attack (pitching down) will result in a speed increase, but then if you're also pulling power back, perhaps not. Flying is the art of managing the responses you can expect from the airplane in the context of the environment in which you're operating. For example, on a calm, cold day you might expect the airplane to nose over slightly and go down when you pull the throttle to idle during an approach. On a hot day in the desert, you may find that due to the environment and thermals, you're going up and speed is increasing. So it's what you expect the airplane to do, coupled with the reality of what's really going on.
Don't get locked into a rote formula of pitch for this, power for that. Don't get locked into a practice of always landing with flaps, or full flaps. You've got all kinds of flexibility in a light airplane. Use it.
Be careful with slips. I was a slipping fool for years. I grew up as a kid flying airplanes with no flaps; slips were the order of the day. I also grew up working on airplanes, and have seen what little bit holds the vertical stab onto the airplane, and the damage that can be done to that little bit. I've seen cracked bolts and vertical stab attach brackets. I've seen damage to the airplane, fatigue, cracking stress. There's a lot of stress on that vertical stab when you're slipping.
I used to slip large, four engine airplanes, fully cross controlled, down canyons while working fires. I threw them around like a super cub. I don't do that anymore. In fact, if I do slips any more in any airplanes, they're mild at best. I learned after many years, many thousands of hours, and a lot of hands-on inspection and maintenance that what I believed as a kid isn't necessarily the best or safest way. You should be able to slip, you should understand the slip, but you shouldn't have to slip, if you can help it. It's better to plan ahead so that you don't have to.
When you do slip, however, remember that unlike adding flap (assuming you're in an airplane that has flaps), the slip is "free." You can throw sink into that approach and pull it out with abandon with a little cross-control action. Don't want the drag and the sink any more? Release that rudder and aileron, and it's instantly gone. You can't do that by retracting flaps; you lose lift and increase sink. Coming out of a slip does just the opposite; you're increasing lift without the penalty that comes from retracting flaps.
The notion of always being in a position to glide to the runway has always struck me as a foolish idea. There are many aircraft and many situation in which one can't glide to the runway. I've heard a lot of instructors insist that their students always be in a position that they can glide to the runway. While I'll fully support the position that one should always be able to glide to a landing in a light airplane, there's absolutely no reason why one should always be able to make the runway. Think about it; two minutes after you take off, unless you're staying in the traffic pattern and flying a tight downwind, you're not going to "make" the runway. Why should it be an issue when you're approaching to land?