That's really up to you to decide, because it depends on which features are important to you, as well as which keyboard you prefer in terms of overall sound, overall feel, etc.
I would strongly recommend that-- if at all possible-- you play a PSR-I455 firsthand in a store, at a friend's house, etc., before you decide one way or the other.
You should also do a detailed comparison of their specifications. Even a brief comparison of their specs shows that the CTK-7300IN boasts more features than the PSR-I455 does-- 2 times the polyphony, drawbar organ sounds with 9 sliders, a variety of DSP effects, a modulation button, 3 times as many registrations for saving custom setups, plus the ability to save 100 user tones and 50 user drawbar organ tones.
So if you replace your CTK-7300IN with a PSR-I455, there will be some things that you'll lose, and it's up to you to decide how important those are to you. On the other hand, there must be reasons why you're considering replacing your CTK-7300IN with a PSR-I455, so again it's up to you to decide how important those are to you.