metabolic slowdown is blown waaaaaaaaaaaaay out of proportion. yes is slows down eventually, but it doesn't stop. so either way if you reduce calories again you'll lose more fat.
if it does slow down quickly while dieting you have bigger issues than being overweight - your thyroid is about to pack in 
for example i was dieting on no carbs or fats mon-fri, then lots of carbs and fats sat and sun for 6 months - when i got blood work my thyroid was perfect. despite losing over 50lbs.
what happened to the slow down there ? 
Using yourself as a baseline for all mankind is a bit absurd. Also...I don't know about other variables in your habits, (exercise type/frequency, etc), so there may be more to the story.
Also I never meant to imply that metabolic slowdown is a huge spectre of impending doom, about to swallow up any would-be dieter, just that it is a mechanism that the body has in place, and it does have to be factored in. I have found that it is easier for me to lose weight, by eating small amounts constantly, and revving up my cardio. I actually seem to be improving my metabolic rate by increasing my calories as apposed to restricting them.... Why is this... who knows, but suffice to say that the hormonal makeup of an individual plays a great deal into weight loss/gain.
To keep it simple though...It is good advices to suggest that one should run a deficit, either by restricting calories, or by keeping calories steady, but increasing cardio, (which would also put you in a deficit, but IMO is generally a superior approach, as it will keep your metabolic rate up, and would make matters more efficient.)
I remember a while back reading that Jay Cutler would simply keep his calories steady for as long as possible, but increase his cardio output, until he no longer saw results, and would then, and only then, start restricting calories. He said that he felt that he held on to much more muscle this way, and that it made dieting easier....for me its easy to see why this would be a good approach.
Nothing is set in stone however...and the main thing is to again be pragmatic, and make personalized adjustments as needed. As long as you don't make any sudden drastic changes, and are willing to be honest about assessing your progress, or lack thereof, this shouldnt be overly complicated.
Of course when a lot of androgens/insulin/GH/etc are involved in the equation, then that has to be factored in.