Okay so here's the thing...Every Liger insert has a perfect 'thing' it does...well...perfectly.
This is true for each size too tbh.
The more I use them the harder it becomes to actually even fathom picking a '#1 Favorite' combo.
The 30mm is really sick. I've used it almost every day since it arrived just to 'watch the magic happen' (so to speak) and it turns heads so hard it's gonna give people whiplash.
If you like watching the melt and the vapor there is literally nothing better I've seen, used, or heard about.
I use it for top down melt videos and larger dabs. If you watch
this video I posted awhile back (this was .3g of shatter) you can see why the 30mm is great for big dabs. You can drop it all at the back half of the nail and then as you dab it pulls the product over the rest of the dish via the air being pulled through the piece. You can see the whole dish vaporizing at once after it fills the bottom of the insert.
SiC for globs or durability, quartz is the jack of all trades (easy to clean, good flavor, great at nearly any temp) and usually ends up being my daily driver for just staying medicated. But then again low temp terpy dabs on the Sapphire are...just so packed with pure, wonderful flavor. Never tasted better.
The 20mm is just a perfect 'all day universal fit' (sort of the way quartz is, too) for me. I can do bigger dabs if they're necessary (ie. my ptsd issues, panic attacks, morning arthritis pain, etc.) but it works great for anyone that comes along not necessarily familiar with dabbing (the 30mm can be intimidating for newer people especially). Takes a little less lung for 'minimally medicating' dabs which is welcome.
I've used the 16 in the car a few times already, tbh. I feel like that's all I need to say. The 16 is the perfect like...single stage Toro rig nail. Small dabs, huge flavor while being lighter and easier to fiddle with. I'm still looking for the perfect 3-5 hole diffy to pair it with.
TL;DR - You really can't go wrong with a Liger, tbh.