you can't compare as they aren't sized the same way and an identical program on both won't use the same memory space either...You could compare speed or time to execute some fonction etc...To make a real comparison, you would need to program both for the same thing and put it side by side and check for memory usage and speed of scanning etc..
These days, i don't know for Omron but you would need a very very large application to run out of memory like it could happend in the past, it usually run out of i/os before memory. The 1214 is great for a stand alone machine but if you are looking to control a whole plant, you should check for a 300 or 1500 plc.