So the new PRS SE Custom 24 is on sale now and the previous version has been discontinued which means it's on sale at my local guitar shop. The old version is £399 and the new model is £649.

Is the newer one worth the extra £250 or should I just get the discontinued one?

The only differences are the new one has a partially carved top and has a coil tap/split. (also a different pickup selector but that doesn't really make much difference to me)
Only you can decide how much a guitar is worth to you.....
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I've HEARD that the new SE CU24s are significantly better than the old ones....
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The old ones are only cheaper because they have been discounted for clearance. The new once do seem better. I image the bevelled top will be more comfortable and the pick ups have push pull coil splitter, so you can achieve a wider range of tones. The old ones did not have this.