Heck, Dim Shield is even more PC-resistant than Titanium Shield. You need to destroy 6 Dims compared to at most 3 Titaniums in a deck.
IMHO, this is a completely wrong way of thinking because:
1) Titanium Shield can be as PC-resistant as Dimensional Shield. Just include 6 copies of Titanium Shields in your deck! If you include just 2 Titaniums, it is either your fault or 2 copies of Titanium are enough to protect you, so you have 4 more free card-spaces in your deck to add something more useful.
Optimally, you want to play dim shield once every 3 turns. If you have 6 dim shields in your deck, roughly every 5th card is a dim shield, and you probably start with a dim shield in your opening hand. Thus, unless you are drawing a f-ton of cards, the optimal number of dim shields in your deck is 6, regardless of PC. Decreasing creature damage by 100% over the course of your chain is likely worth 6 draws. Against 3 PC, you still have a reasonable expectation of being protected for some of the game.
With titanium shield, calculating the optimal number of titanium shields in your deck is more complicated. You have to consider how much damage you will take before you draw the first TS. You have to consider how many dead cards will glut your hand if your opponent has no PC. Adding more TS beyond what you need to counter PC is worse than a diminishing return. 6 TS is actually worse than 3 TS unless your opponent has PC because it is 5 dead cards in your deck. Thus, the optimal number of TS is going to be something like 2-3 if you don't expect PC, and 4-6 if you do. But alas, you can't predict whether you are going to face PC (or how much) so you compromise and put in 3 TS. 3 TS is nearly worthless against 3 PC, and has a small but annoying chance of glutting your starting hand against no PC and an expectation of a dead draw at some point in the game.
It gets even more complicated when you put in PA with your TS. Now you have to consider the chances of glutting your hand with PA. If your opponent has no PC, every PA is a dead card. Ouch. If your opponent has PC, and you draw the PA before the TS, it is dead until you draw the TS. If you draw a TS before the PA, it is dead until you draw the PA! And finally, if you draw a TS after a PA + TS, it is dead. In practice, outside certain niche decks, you never see more than 1-2 PA, and usually only in support of better cards than TS.
That is the beauty of 6 dim shields. They are almost never dead, and if your opponent doesn't answer them, no creature damage!
2) Titanium Shield is permanent. After 1,000 turns it would be still there. Dimensional Shield lasts only 3 turns.
Unless it was blown up by PC, in which case it lasted 0 turns. Oh, and it also will last 1000 turns in your hand as a dead card if you've already drawn a TS.
4) Titanium shield is cheaper than Dimensional Shield (4
is better than 6
), so it is easier to replace a destroyed Titanium than a destroyed Dim Shield.
This is your best point. But two things make it not matter:
1. As I have explained above the optimal number of TS in your deck is 3, so you are likely going to have to wait for much of the rest of the game for your 2nd or 3rd copy. But since the optimal number of Dim shield is 6, you will only have to wait about 5 draws to replace it.
2. They are both getting owned by the PC. 4
![Earth :earth](https://elementscommunity.org/forum/Smileys/solosmileys/../../../images/Misc/earth18x18.png)
is still vastly more than the typical cost of PC.