Absolutely go with the 350. The difference in screen quality is amazing. The reflow for PDFs works if the PDF is text only and searchable (not an image).
Also, I'd recommend Calibre software to manage your library. It's free, it's powerful, it's well supported by lots of developers, and can turn old lit, pdb, rtf, txt, etc. files into better formatted ePubs. Nothing can work magic on a PDF where the text is images. A horribly formatted book will continue to be horribly formatted until you put some effort into fixing it, but Calibre can sometimes convert books into something more readable.