Manga version is much better than the anime one, for instance in the characters' development department (well, at least concerning the 'good guys'). Among the biggest and better differences, Usagi/Serena actually grows up as a person, Mamoru/Darien has both a more than decent personality -ok, I love the guy ;p - and more than decent powers not to mention a better fashion sense. And Chibi-Usa/Reenie is a quite likeable character, and so on... .
Moreover, the monsters-of-the-day are almost absent (hooray), and the 'Power Ranger' factor is thankfully very low (double hooray): you can appreciate more and more the lack of these elements as the story goes on 😉.
Emphasis on 'as the story go on' because the story starts as fairly episodic, it's only later that you start to see the big picture.
And, boy, what a BIG picture turns out to be, and a surprisingly coherent one (considering the number of characters alone, it's impressive. Add to this the work overload - the author ended up working contemporarily on the manga, the anime, the musical version, then the live action... all of them with some major plotline and characterization differences -. Sometimes it's quite easy to see the artist just went with the flow with her golden egg goose, but she managed to wrap basically everything together in the end (and the loose ends are absolutely yummy: no wonder Sailor Moon has a huge fandom and fanfiction base even now. With some good-to-excellent writers on top of it).
Some plot-twists and settings in the manga were just great and unexpected (especially in the last two arcs -aka the (in)famous Super S and Stars anime seasons) and IMO basically balanced out and/or even redeemed some of the plot devices repetitions and shoujo clichès.
On the other hand, of course there are some plot-holes and the aforementioned loose ends; the villians are not developed as they could have been (and sometimes as they should have deserved too); the art may not be pleasant to everyone (both style and quality can vary a lot too. My appreciation of it varies a lot too up to the moment, and I 'm supposed to be a hard-core fan).
In the end, it's a series with an amazing and fascinating potential, that puts together both East and West in regards to myths, folklore, and literature references/influences, not to mention it weaves together different manga genres. Sometimes the mix doesn't blend very well, but when it does, it's great. Personally, I still love this story: both thanks to and in spite of the contradictions due to all the different cultures' elements and the 'Romeo and Juliet + superheroes action' core.
So, yes, I'd suggest you to try the manga (unless you can't stand romance at all, because you'll find plenty of it 😛 ). The hard copies for English audience (and not only for English people :/) may be hard to find due to the whole matter of copyrights controversy between the mangaka and the publishing/anime companies. But the manga has now been completely scanlated by Royal Orange, and you can still found the torrents for the Mixx version around the web (hint: Google search for 'Sailor Moon Center' or 'Anime Avatar')
Overall Rating: 8.0/8.5. It had the potential for a 10 though.
I'm rating it 10 nonetheless for the sake of global rating in the page.