Calibre is more efficient than diva and dracula. The calibre rule deck file has better readibility than that of dracula. But diva is very convience for small layouts.
not realy, the results are same ,but is more fast and cheap . mentor tools are more cheap than cadence . my company migrate fom cadence to mentor because of the price of the license
I have seen Assura have segmentation faults (crash) or lock up with larger designs. Calibre would run on the same designs with no issue. The syntax for the calibre rule decks is also easier to learn - at least it was for me.
The Assura user interface is friendlier but Calibre is not bad.
Please see the Image , this is a post layout simulation result at 6 GHz for a CMOS Mixer with Calibre, Assura and Schematic(without post layout), as you can see it seems that both Assura and Calibre have the same results. (Technology : 90nm)