well, since everybody is giving their opinions, here is mine: always strive for new. Then test it. This is basic UX, you should test everything.
As for the new vs conventional part, let me explain this with a very common example: music.
In music, you have composers/creators, you have interpreters and you have a mix of both.
A composer may or may not be a good interpreter, but he creates, therefore you could become The Beatles.
An interpreter strives to be great at the interpretation of its instrument, but she doesn't create. Hence, she might be regarded as a great player, but she will never be the Beatles.
Most of us will never be The Beatles, neither amazing interpreters. So as you can see, both are needed, and both are amazing at its own field.
In design (whatever kind of design you want to mention), if you create something new, you might lead the pack. If you take the philosophy of ALWAYS strive for new, then you'll probably create something meaningful down the road, maybe revolutionize the world, who knows?
But if you can't or don't want to be innovative... the world always needs good interpreters, there's not shame in it, being an amazing designer that never creates anything but it's spectacular at working with convention and rules is something great. OK, you won't create the new Facebook or the new iPhone. But you'll be amazing at implementing things.
However... testing is everything. This is something the musician and the designers know, no matter if creators or interpreters: there are ways to measure the success of an idea. So make sure to test everything to avoid failure.