Site Pages vs Pages Library

Hi

I've noticed that if a Page is created in the Pages Library it cannot be edited in SPD however if a page is created in Site Pages Library it can.

We have used pages library as it offers page layouts but dont like the fact the page cannot be edited in SPD.

We dont require the publishing feature apart from the page layouts aspect, if this can be achieved in site page then this would be a better alternative.

Currently we have added webparts to pages in pages library using ui.

And advice?

Thanks