Let's look at this from the stand point of speed at 90 rpm and go back to my example. With a 3x7 system in the 46/24 gear at 90rpm, you'll be traveling at 14 mph. When you shift from the outer ring to the middle ring, say in preparation for a hill, if you maintain 90rpm the 36/24 combination give you a speed of 11 mph. You could maintain the same speed by increasing your rpm to 120 if you wanted to or had to. But the speed differential is small enough to that you'll slow down quickly enough and can maintain a comfortable 90 rpm.

With the double and a 10 speed cassette, in the same 24 tooth cassette cog, you'll be doing 13 mph. Changing to the 24 tooth inner drops the speed roughly in half at 90 rpm to 7mph. If you increase your rpm to 120, you'll be able to develop 10 mph and you'd have to pedal somewhere around 140 rpm to get to 12 mph. I can do 120 for a little while but 140 is just way too fast and too uncomfortable for even short times. About your only option is to let the bike slow down to around the 90 rpm range and just eat the loss of momentum.

If you go the other way...an upshift...let's say that you are tootling along at 12 mph at 90 rpm in the small ring for whatever reason (this will work with any speed in any gear combination but let's just pick one). That's going to be a 24/14. You upshift to the outer ring. If you could maintain the 90 rpm...you won't be able to...your speed would jump to 21 mph. In reality, you rpm would drop to somewhere around 50 rpm. That's mashing range. To get your rpm back up you'll have to either drop back down to the inner ring or make 4 downshifts on the cassette.

With the 3x7 system, you could be rolling along at 11 mph at 90 rpm in the 36/24 gear, upshift on the front to the 46 and you'd be at 14 mph while still maintaining an rpm of 90. In my opinion, I'd prefer a single upshift on the front chainring to an upshift on the front chainring and 4 downshifts in the back.

While the 10 speed system might be marginally better than an antiquated 7 speed system, when it is compared to a modern system or even to a triple crank and a 10 speed cassette, it falls far short. A 42/32/24 (or 22) 10 speed system would be almost ideal. It splits that 60% difference between the compact nicely in half.

I too go by pedal feel but I don't know of anyone who downshifts until they can't downshift anymore. Most people will learn that downshifting until you hit the largest cog on the cassette leaves them in a bad gear combination where further downshifting only leads to having to do high rpm to maintain speed. A bike drivetrain isn't linear like a car's drivetrain is. It doesn't take too much time to learn the difference and how to make better use of the bike's gears. You don't have to ride like you are in the Tour de France or like the bike is a car to appreciate a good gear pattern. My objection to the compact double idea is that the gear pattern are like a linear gear pattern in a car...just really poor versions of it. If you look at the speeds, the gear inches, the gear ratios or whatever is you favorite flavor of gear calculation, the compact double system is like two entirely separate drivetrains. It's got a high range and a low range and nothing in between.

That's the point to any triple crank, isn't it. You, with a double system, can only shift one time to go from high range to granny. It's a big 'KACHUNK!' and it goes from fast to slow. A triple has steps so that the rider can choose gears in between high and granny to fit the terrain they are riding.

Yep. Tighter ratios than a 3x7. But not tighter gear ratios than a 3x9 or a 3x10. Just fewer choices.