Do any of you know which one is stronger or I guess it varies from person to person as each of our bodies react differently. I know both are the same class of drugs "calcium channel blockers" but wondering why one is 2% and the other is .3%.
The main reason as I have read elsewhere in this forum is the Diltiazem itch. I have it too. However, so far I don't have the itch with Nifedipine but Diltiazem seems to work better for me at relaxing the muscle. So if they are both the same class of drug shouldn't I be OK with Diltiazem if I am OK with Nifedipine?
I tried both Diltiazem mixed with gel and lidocaine, both same result...ITCH. Has anyone tried Diltiazem at a different compounding pharmacy and find it to be better?

I have only used Nifedipine, no experience with Diltiazem. My Nifedipine is .4% though. My pharmacy that I get the Nifedipine at always has it in stock already compounded. The pharmacist told me they have a lot of customers using it, so they keep it well stocked. So I guess .4% must be pretty common dosage for the Nifedipine. I do not have any problems with itching from it, it is also mixed with lidocaine. I have heard of some people developing a 'caine' sensitivity, but if you had the Diltiazem mixed with gel and had the same result with the itching, it might it may just be your reaction to the Diltiazem.
Good luck figuring out what will work best for you.

Another thing I noticed is that the Diltiazem and the Nifedipine I get is in a smooth vaseline form (kinda like a smoothie texture) but after about 2 weeks it starts to get a bit more watery and pasty. I asked the pharmacy if I need to put it in the fridge but they said no just keep it at room temperature, but with the summer weather, my house gets pretty warm throughout the day even when I put it in the coolest room in the house. I wonder if this slight change will alter the effects of the drug?

I wouldn't read too much into the concentrations or the fact that they're in the same class of drugs. It's all about how your individual biochemistry reacts to the drug. 2% is a higher concentration than 0.3%, of course, but what if Nifedipine is much more biologically active, is eliminated slower, or has higher serum bioavailability due to better gastrointestinal absorption? I don't know any of that's actually true, but it's possible. There are lots of factors to consider, so I'd base my judgment on which you feel like is doing you more good.
FWIW I tried all of the typical fissure ointments and liked nitroglycerin the best (most effective), followed by Diltiazem (somewhat effective but with some local skin irritation), and finally Nifedipine (no side effects but also didn't do much for me). Others have the order reversed, however, so it all depends :)
I'd wager that the compound becoming watery after a while is a non-issue. That sounds like the base breaking down a bit due to either heat, moisture, or light exposure. It probably makes the stuff a bit trickier to apply and less likely to adhere to where you put it, but aside from that I doubt it would affect the active ingredient's potency.
As for the itching, IMO it's hard to say what's causing that. It could be the Diltiazem, the lidocaine, or the base. The only good way to figure out would be by process of elimination, e.g., leave out the lidocaine next time for example (or if you're really curious maybe buy a small tube of OTC lidocaine from the drug store and put a dab on your finger or arm to see if you're allergic to lidocaine). Mine never had lidocaine and I also didn't find lidocaine to be very useful at all for fissure pain anyway. A different pharmacy may use a different base, so it's possible that switching pharmacies would alleviate the itching, but that's probably something you'll never know unless you do it, unfortunately.