Here we go again.
Firstly, Rocket. You've quoted the lift equation, well done. The problem is we are not talking about lift alone, we are also talking about thrust. You might remember there are 4 forces acting on an aircraft (plus the tail balancing force). If you take away the issue of thrust to overcome the drag, you are talking about gliding - hence of course you have to use attitude as there is no thrust to overcome the drag.
Graeme. Which way will it go? Depends on the thrust/drag configuration of the aircraft, the centre of pressure (eg swept wings). So for those giving examples, that may be true for that type, but don't think that is the case for all. What WILL happen though is if you maintain the attitude, the aircraft will slow down, and of course at some stage you will have to lower the nose to keep flying speed to avoid a stall, because you no longer have thrust to overcome the drag. For many RA/GA aircraft, the thrust/drag couple is designed to do this automatically (idiot proof?!) so the nose is likely to drop to maintain speed. This is a design feature, not an aerodynamic principle.
Now, for the students reading this.
I really, really don't want to get into complex aerodynamic debates here because from what I've seen, there are some basic misunderstandings of aerodyamic principles.
My advice is to take advice from the real experts - those who have studied the subject in detail - experienced airline, military (such as Mr Kruse - one of the most successful GA instructors), competition aerobatic pilots, or suitably qualified professionals. Please don't take advice from those who have been shown one way decades ago and believe anything else is WRONG.
When I started flying I was taught to use attitude for speed, and I did so for many years, until an aerobatic instructor said "let's try another way." Like some people here, I thought the guy was an idiot and was clearly WRONG because my other instructors taught me differently - I'd managed OK so far. Until I actually took the plunge and did what he suggested. It worked, and worked far better than the old way.
Yes, of course you can get by using attitude for speed, it works - up to a point. If you are only ever going to fly as you are doing now, stick with what you know if you are not interested in trying an alternative. But when you start flying something of higher performance (or if you start flying instrument approaches) that technique fails.
My issue for the students is why not start out with a method that you can use in everything from Jabirus to A380s to fighters?
For those who are using attitude to control speed on a powered approach and say anything else is WRONG, have you actually tried both techniques?