Locking some decks out of their mana generating artifacts can also offer you a quick and easy win
Some players dont like when a counter spell has the ability to counter it built in, but in my experience you either get the counter, or you screw up a turns mana unless the opponent had an overabundance of mana anyway
He can also only make token copies of creatures, while Saheeli lets you make copies of any permanent
Personally, I love the dynamic look of these, and the way they really evoke that comic book feel
The first three are more likely, but the final one can have some value here and there
A lot of the time when Im evaluating cards Im thinking whether they will fit into an existing deck, or go into one of the deck ideas I have