[smsm42]

Practically, the difference is not that big. There are many sounds English letters can't encode, and for others it cheats by saying "let's pretend th sounds like this, despite it having little to do with t or h, and then zh sounds like that, and ae like this, and so on". You could do the same with a syllabary - and to some measure Japanese does, aided with special marks and other tricks, but as English inevitably misses some sounds, so does Japanese. It's inevitable - look at IPA symbol set to see how many there are needed, and I'm sure even that doesn't cover all the possibilities.

What you lose with syllabary is to be able to encode some patterns - like Czech "strč prst skrz krk" - pretty much no way to encode it in Japanese I think, unless you resort to a lot of cheating like inserting "u" everywhere and then declaring "u is silent" (which is pretty normal for Japanese in general but in this case kinda looks like cheating). But tbh English encoding wouldn't adequately describe how it's pronounced either.