I don't recommend either. Each of them have very significant flaws. There is no point in using them over better walls and stallers, especially not if you are playing competitive Pokemon (which, by the looks of things, you are). I'm also slightly confused as to what you want me to critique, you have "wall" in your title but you seem to want a staller. I'll just try a combination of both.
Also this is going to sound harsh so be ready for that ;)
Shuckle
- Base 230 Defence and Special Defence may look appealing, but it isn't after you see Shuckle's HP. Base 20 is not going to get you anywhere at all. Shuckle's bulk isn't any better than most other walls, simply because its HP means each hit deals a much higher percentage of Shuckle's health.
- Bad typing. It resists two types, one of which being very uncommon as an attacking type. It gets hit super effectively by Steel, Rock and Water, with the latter two being very common attacking types.
- Cannot deal any damage at all without using a gimmicky move like Power Split. This means it relies on Toxic to deal any damage, which will slow down the battle and will mean Shuckle will sustain lots of damage as part of stalling. That particular set is also shut down by the extremely common move Taunt. Infestation won't do jack.
- No reliable recovery. Rest puts you to sleep and turns you into setup fodder, which is the last thing you want in a competitive battle against an intelligent opponent.
If you're going to use Shuckle, use a set that isn't as gimmicky as that one (although that's hard to do as Shuckle is a gimmick in itself). Use Sticky Web and Stealth Rock at least.
Cradily
Much better Pokemon than Shuckle with more balanced stats and a more usable set of offensive stats. However, it is outclassed in every way by Ferrothorn, who boasts even better stats, a better typing with more resistances, a resistance to Stealth Rock, decent attacks in Power Whip and Gyro Ball and more. The only thing Cradily really has over it is good recovery, but that isn't enough reason to use it over Ferrothorn.
This is the set that gets Ferrothorn a lot of attention (stole this from Smogon becuase I'm lazy like that):
Ferrothorn @ Leftovers
Ability: Iron Barbs
EVs: 252 HP / 88 Def / 168 SpD
Impish Nature
- Stealth Rock
- Leech Seed
- Toxic
- Gyro Ball/ Power Whip
Ferrothorn is one of the most well known walls/ stallers in the game. It packs fantastic defences, access to excellent support moves and it also has a good typing to go along with it, unlike Cradily who also packs just two resistances and four weaknesses.
For some other recommendations on stallers and walls, see this article by Smogon. It's for gen 5, but most of the Pokemon there are still relevant in their own tiers.
As for status Pokemon to support them, paralysis support is very useful for stallers that are generally very slow. Sleep is nice for just about everything, I don't think I need to explain that. So yes, basically, but don't do anything drastic like remove a Pokemon on your team just so you can have a Pokemon with the move. You're putting too much effort into your stallers if you're doing that, support your other Pokemon as well.
