Not only is Hebrew more compact, but ancient Hebrew is much more “blocky” and simple than any of the forms of ancient Egyptian.
Hebrew caracters with no vowel markings are indeed compact. However, once you start adding tittles and other minute markings, you've got a major problem for engraving on metal plates. Also Hebrew characters are written in a variety of stroke widths, another major problem.
You do not seem to catch the significance of "reformed" Egyptian. While you are correct that ancient Egyptian writing is not simple, Chinese caractors are also complex, and a modernized and simplified form of Chinese caractors does exist. One could even call that simplified Chinese "reformed".
The Book of Mormon plainly states that no other people can read their reformed Egyptian caractors, which means that Book of Mormon authors and scribes invented reformed Egyptian specifically for their recording on plates. They would obviously create a caractor set that would not, as in Hebrew, have various widths of stroke nor a system of tittles and other time-consuming minute markings.
I only wish that the 8 witnesses had been a little more specific in describing the reformed Egyptian that they looked at: "and as many of the leaves as the said Smith has translated, we did handle with our hands: and we also saw the engravings thereon, all of which has the appearance of ancient work, and of curious workmanship".