I agree with all of the above.
Looks like it is on sale for $13 - get it and see how you like it.
You probably can't find a source comparing them because they are both fine solutions - the choice of one or the other is a personal preference.
The "14" in each means 14 teeth in the smallest (fastest) gear. The two parts will function identically there.
The "28" and the "34" refer to the number of teeth in the largest (easiest to pedal) gear. Using the 34 gear on the 14-34 will be noticably easier to pedal than any setting on the 14-28.