You don't need to buy a new phone to improve the recording quality. Your iPhone has several mics - and Tape It combines them to record in stereo.

Put some headphones on and listen to the difference. Here's a vocal from Julia Jonas recorded in the standard recording app:

Julia Jonas Voice Memos Example - short.m4a

And here's the same line recorded in Tape It - on the same phone:

Julia Jonas Tape It Example - short.m4a

Stereo makes such a difference: when your recordings sound better, you'll listen to them more often. Quality matters for every recording, even the rough ideas.