Ok, let's compare Darksteel Colossus to some of the more popular tinker targets of the day.
Platinum Angel is better than DSC:
Opponent has ample attackers and one blocker is inadequate to prevent taking lethal damage
Dragon has decked you and you have an active welder
When card is in hand and seven mana is availabe but not eleven
When card is in hand, active welder is in play and some form of discard is available
DSC is better than Platinum Angel:
Opponent has active pentavus
Opponent has ample non-STP removal spells and you have no counters.
Pentavus is better than DSC:
Opponent has ample attackers and one blocker is inadequate to prevent taking lethal damage
When card is in hand and seven mana is availabe but not eleven
When card is in hand, active welder is in play and some form of discard is available.
Attempting to set up a hard control slaver lock.
Opponent has Smokestack
Opponent has Tangle Wire
DSC is better than Pentavus:
Opponent has active pentavus
Opponent has ample non-STP removal spells and you have no counters.
Mindslaver is better than DSC:
Opponent has ample targeting card drawing spells such as Ancestral/Deep Analysis
Opponent has fetch lands
Opponent has Removal Spells or sacrificing effects (Smoke Stack, Sacrificing creatures)
Opponent has very slaver vulnerable cards (Dragon Combo, Psychatog, Necropotence, Hymn de Tourach, Bazaar of Baghdad)
Opponent has Land Destruction lands (Wasteland or Strip Mine)
When Mindslaver recursion if not infinite recursion is available
Opponent has active Goblin Welder
Opponent has powerful spells that you can waste (Yawgmoth's Will, Berzerk)
Too many smaller situations to name
DSC is better than Mindslaver:
Opponent has stifle
You do not have the four mana to activate the slaver
Opponent has very few resources for you to make use of or remove
Opponent has Juggernaut and neither you nor he has any answers to Juggernaut
Memory Jar is better than DSC:
When you have very few cards
When Many spells can be cast after the jar has been popped
When placing cards in your graveyard can have positive effects (active welder, Madness spells, Flashback Spells) and your opponent does not
The primary win condition of your deck is to cast a storm spell
When you can recur Memory Jar
DSC is better than Memory Jar:
When no spells are likely to be cast after popping the jar
When placing cards in your graveyard can have positive effects for your opponent (active welder, Madness spells, Flashback Spells) and you do not.
When your opponent has stifle
When your primary win condition is attacking with large creatures.
I honestly think that in all these cases DSC is the inferior of the bunch, TAL's control slaver build runs all the compared cards mentioned above and fits your conditions for playing the combo,
-If you have 5 moxen in your deck, a lotus and sol ring/crypt.
-When you have tutoring to search out the tinker, or alot of draw/discard.
-When you have thirst for knowledge to get rid of colossus, or brainstorm to put it at least 2 cards down. Or you have draw 7s to discard a colossus in hand (see ravanger affinity).
and the times where DSC would be a better tinker target than any of the four listed above is very slim and many people already complain that there are too many "dead cards" in this deck that can destroy you're opening hand without a thirst for knowledge and the draws are too inconsistent.
