So I finally managed to scrape up a box of these guys, but am not sure how to build them. I'm leaning towards Terradons with Sunleech Bolas, but decided to dig through the archived posts for advice. Turns out the last time anyone really discussed this was 2016! Now that 2nd edition is out along with all the "fun" errata, I'd like the opinions of people who have used them. Which seem to work better? I'm going to get BOTH eventually, but for now I only have 3 so I can only make one or the other...
I actually had this come up with a friend a while ago so I have a few things to say on this. So this is really dependent on what you want. If you play many chaff units or units that don’t deal much killing power, hands down ripperdactyls blow terradons out of the water. They are simply superior in terms of killing power. However that does not mean terradons are useless. If you play units with decent killing power (saurus warriors) then terradons can be useful. They are very good skirmishes and distractions capable of dealing some damage to a point where your enemy might devote some resources to try to pin them down and kill them.
At the moment I have: 10 Knights (old skink cold one riders), 5 Knights (plastic), 10 Saurus w/spear (obviously I need more), 20 Skinks, a Troglodon, and a pile of characters (Priest, Starpriest, Astrolith, Sunblood, and Scar-Vet on Cold One). I'm planning to get another SC box when I have the money (game stores locally were out and at the time I had to buy local or I'd have gotten that instead of the Terradon box), but I don't have any really killy units at the moment. I was leaning towards Terradons so I could use them to support the Knights on a charge.
Hmm, knights are ok but you really should not rely on saurus knights. They were once good, but now really, really, REALLY suck. They are to slow, they lack rend, and the power of a good charge. At this point you can really only use them as meh skirmishes or chaff. I cannot emphasize this enough: they cannot be used to be effective killers. If you want good cavalry that kills then definitely use the rippers. However depending on what you build on next you could viably use terradons. If you expand on your saurus then go with the terradons, if you go for skinks then do The rippers. Edit: sorry if I seem negative on the knights but I would hate to see someone else be disappointed by them.
Oh no, I know how the Knights work - or rather, how they DON'T work. But they're what I have. To make 1000 points I have to use almost EVERYTHING I own, which happens to be 15 knights, 10 saurus, 20 skinks, a Troglodon, and a smattering of characters. Thing is, if you can buff the knights with a Skink Priest's abilities and the Starpriest's serpent staff, they become halfway dangerous again. Put the skinks BEHIND the knights, unless there's something I missed, the skinks can shoot into whatever melee the knights are in. Priest lets them reroll saves, serpent staff from the starpriest gives them a melee boost. Not the BEST options, but reasonably workable. At least until I can get more minis...
Ripperdactyls will deal far more damage than Terradons. Even without the toad they will average more damage than the Terradons. Rippers also ignore rend 1 make them slightly more durable. The only real advantage Terradons have is their once per game mortal wounds. However, the sheer volume of attacks from Ripperdactyls should allow you to reach similar levels of damage against targets with high saves. The mortal wounds do become superior to the Rippers attacks when the target is something like a SCE Stardrake with its shield that cause mortal wounds back on successful rerolled saves.
I would like to add that sometimes summoning Terradons can be a good idea: When using javelins they have ranged attacks with just enough range so they can shoot in the turn they were summoned. So if you lack ranged attacks and just want to do a wound or two on some enemy unit (to finish off some hero for examlle) then summoning three Terradons can make a lot of sense. As for their bombs: I noticed that people who know about the bombs (make sure to tell your opponents) tend to fear those more than they probably should, and might tend to put more resources into killing the Terradons than they should. That makes them pretty nice for harassment. (Also they look a lot better than Rippers IMO).
Rippers have NEVER let me down. They hit like a truck with the toad nearby. But don't use them on anything with a save better than 4+.
Rippers are currently better in most situations due to the changes to shooting. Those changes took away the one advantage terradons had (shooting into your opponent's backline thus forcing your opponent's supporting heroes to back up further or risk dying). They still have some uses like @Aginor & @LizardWizard mention with summoning and their mortal wounds, also they're a little bit cheaper but it's quite limited right now. They need a buff or two to help them distinguish themselfs from rippers.