i think garu hit it on the head.
a few things to keep in mind:
1) backhand throws ALWAYS have more distance potential than sidearm throws (world records are 820' and 517').
2) a strong backhand technique is a necessary part of your arsenel since a lot of finesse shots and most putting forms are modelled after a backhand throw.
3) a sidearm is a very nice luxury to have.
that being said,
i will say, yes, it is worth it in the long run to struggle through learning a backhand technique.
if you (or someone you know) play guitar, i compare backhand and sidearm to learning guitar through traditional instruction vs. power chords. while power chords will yield a much better result at the beginning and will keep you playing and entertained, the real ability comes after you learn the fundamentals. however, even after you learn the fundamentals, you will still use power chords when they are appropriate/necessary.
while sidearm may give you the best short run results, the plateau comes much faster. it's never bad to have a good sidearm. it's always bad to not have a good backhand, but backhand will also take a much longer time to perfect and hone.
my recommendation is to work on the backhand but still throw the sidearm when appropriate (behind a tree, dogleg right shots, etc.). however, i would say to try to stay out of the habit of falling back on it as a crutch. i know a lot of people who made the transition and every time their backhand started to go awry, they would immediately default to sidearm for the rest of the round and this hindered their development. also, defaulting too often to a sidearm often will neglect learning a good anhyzer shot.
if you reach a point where you are equally good at both of them, then use whichever you feel is best for the situation.
i will give the warning though, that 400' sidearm technique is prone to blowing out the elbow, an injury (which i have had 3 times) that takes ~20 months of rest to heal.
let it be known though, i wish i had a better sidearm