I would go for it. I think the workflow enhancements are well worth the upgrade, but you'll want to read through the updates to see roughly what of the new stuff is useful for you. https://www.image-line.com/flstudio/history.php
Or the quick version:
FL 20 in 4 minutes / in 15 minutes
FL 12.5 in a minute / in 21 minutes
FL 12.4 in 11 minutes
I don't know where you paused, but in particular I found these notable improvements (and this covers pre-FL-20 to some extent):
Per-bar time signature change (you know why!)
Live preview of recordings, and ability to consolidate MIDI into bounced WAVs with undo
Stretch/compress entire groups of notes using right-Shift and click-dragging from the right-hand side. This can be useful for generating polyrhythms.
Mini-playlist preview above piano roll, so you know where you are
New Fruity Delay 3 VST (you'll love it!)
Link a bunch of channels one each to sequential mixer tracks using Ctrl+Shift+L! Really helps when mixing with stems.
Ghost notes (maybe new to you?), great for writing complex harmonies.
Vectorial interfaces for certain VSTs
Hi users of OCRemix!
I've started to work on this kind of project for now. I've used Kass theme and Song of Storms for now. Maybe I'll add something else later too.
It's quite simplistic but I want to give it plenty of "space" to live in. Don't have a clue what instruments I should test to fit in this piece.
Hope you enjoy!
REMIX: https://www.dropbox.com/s/5hqodshhqdj96dn/Breath of the Storm.mp3?dl=0