So I have yet to field Kroxigors, they seem to be a bit of a discussion point in their uses, there are people who swear by them and some that think they are crap. For the cost of one Krox you can buy: 1.5 CoC - Not really a better unit imo, you get more wounds, and a better Str stat (because of GW) 4 Saurus (with Spears) - This is the one that I have issues. You have more attacks, more wounds, and the only down side is S4 not S6, and no fear. Fear is really not that big of a deal most units have a 7+ Ldt and its usually 8, 9 or 10 and most people get some form of re-roll. 3 TG - Here you are getting an equal number of wounds, a better Ws again at the cost of str6, but with the 6 attacks vs 3 it doesn't seem to be that big of a difference. I did forget to mention the move 6 vs 4 for other models With their point costs, meh stat lines, and the fact that they need skinks to soak attacks are Krox really work taking as a unit? you get a fast med hitting unit but the cost is rather steep (95 points for 1 skrox setup, 8 skinks, 1 krox)?
I do have to wonder sometimes if I would be better served with another unit of saurus instead of the 22 skinks + 2 krox unit. They are very close to the same points, but it is worth remembering that they should have different uses. The skrox are fast (march 12" is great for infantry!) and work very very well out on a flank. They can take on almost any flanking/support unit in the game, they can shoot with poison if needed, and they can swoop up a flank then start getting into the flank of your opponents main battle line. They work great as support, but not particularly well as standard main line infantry. Which is, of course, where the saurus come in. They are perfect main line infantry. So the question you need to ask yourself, is what do you need more in your army? For my army, I already had 2 units of saurus and a unit of TG for main line infantry, so a unit of skrox serves me very well doing a different role to what another block of saurus would do. Finally, don't bother taking krox on their own. They will die too easily.
For me, it really depends on my plan of attack, opponent, and personal play-style. Like you said, you have a couple options - one with skinks as shields (skrox) and the other as their own unit. The skrox unit is one great flanking unit. To be able to field krox's without the worry (albiet templates) of being singled-out is quite an attraction to the unit. It's fast moving and hard hitting. One of the drawbacks to this, however, is the potential size it can be to field it as a flanking unit. Table top terrain will play a factor here as well. Add to this a Lore of Life slann with Throne of Vines and the +toughness spell, then you have a good backup block. Also, personally, I really like the fear this unit causes. It's a "free" chance to reduce your opponents ws. So, if your play style is supporting your main anvils or wanting to add to your hammer, this is a decent unit to use imo and well worth the points. Using the Krox by themselves can have it's advantages, but again, and imo, depending on the above situations. With the addition of stomp they can be used to good effects. They will, however, be a draw for your war machines and spells. This is a hard hitting unit that moves fast as well and your best bet may be to get this into combat quick to avoid spells and warmachines. Getting some boosts from your slann will help them out. Personally, I don't use them this way as I prefer the Skrox method. But then again, it's my play style. I think this has potential to be a point sink and would consider using this style situational. Anyways, this is my style of playing them with my opinions. I'm sure others can share their thoughts here as well. - Lord Cedric