If the panel supplies the same mAh rating as your phone's battery, and the phone can take the current (how much current it takes is set by the design of the phone), the battery would charge from 0 [which you should never allow - 40% is the lowest you should drop a lithium battery] to 100% in about 70 minutes.
As far as make, Anker is a good company. I've bought a few of their products and they're well made. (I'll probably be buying a couple of their batteries soon.)
Remember, the rating is for full sunlight at noon on June 21st. or at the equator. Further north or at other times and dates, you'll get less current, so buying a solar panel that's a bit overpowered for your need isn't a bad idea. A little overpowered. Maybe 4000mA or 5000mA. That way you'll still get a normal charge time this time of year at 4 in the afternoon. (Solar battery chargers are rated in mA, not mAh. mAh is capacity, and a solar charger doesn't have capacity, it has current availability.)
A power pack, OTOH, has capacity. A 25000 mAh power pack will charge a 2500mAh battery 6 times before it has to be recharged. (You shouldn't drop the power pack below 40% of its capacity either.) A solar charger can be used to charge phones all day long, as long as the sun is shining. By the time it "wears out", we'll be having "cellphones" implanted in our heads at birth. (Silicon exposed to light produces a flow of electrons. The same piece that's doing it in your charger has been doing it for any part of the 4.5 billion years it's been exposed to sunlight.)