Since there are many Hanlin V3 owners, here is a review of the V5 just for you.
I actually have an EZ Reader Basic and Pocket Pro, but Astak uses the Jinke standard firmware in both.
The V5 is small. This is obvious, but I did not expect it to be as small as it is. If you put the V5 on top of the V3, with the top left corners lined up, the V5 does not cover any of the V3's keypad and its right edge does not quite reach the edge of the V3's EInk screen. Overall, I prefer the look of the V5 - it has the same keys on the front but they seem better proportioned on the V5.
The USB port is at the top on the V5, with no plastic cover. It is USB 2.0, and file transfers are much faster than on the V3. The headphone port is still on the bottom. There are no volume keys on the right side (the earphones have a volume slider), but a rocker switch has been added top right. It provides a 3rd way to page forward and back and also a 2nd OK key (press the rocker in). I like the light touch of the rocker for page turns.
The included brown cover holds the V5 firmly and has a similar magnetic clasp to the V3's cover. However, it is not padded like the V3 version. I prefer the V3 cover, but the V5's is ok and should provide good protection for the screen.
There are 8 grey levels on the V5, and this make a significant difference with some images. On the other hand, the same image is larger on the V3 (due to fewer pixels per inch) and overall I would pick larger over more grey scales.
There is essentially no difference in the user interface or in how ebooks are displayed on the V5 (providing you are using the Adobe Digital Editions firmware on your V3). In particular the font sizes, in pixels, are exactly the same as on the V5. This means that a particular font size will be 83% as tall and wide on the V5 (because of 200 vs 166 ppi), but exactly the same number of words will fit on each line as before and there are the same number of lines per page. Since the V5's screen is smaller, you might have to increase the font size one notch on the V5 over the V3.
There are eight included fonts for TXT ebooks on the V5, and you can add your own as before. There were only two fonts available for FB2 ebooks, and I was not able to get it to recognize my own fonts (which worked on the V3). Adding a font family for MOBI ebooks works on the V5 just as on the V3. The V5 is using a Serif font (Times) for the file system (8 ebooks per page) listing, and I much prefer the San Serif (Arial) used on the V3.
On the V5, I find myself reading ePub in landscape mode. If the available font sizes were a little better chosen I would switch back to portrait. Like all the ebook formats, the ePub font sizes in pixels are the same on the V3 and V5 but they are better suited to the higher pixel density of the V5. Even on the V5, Jinke's choice of font sizes for ePub is far from optimal.
In normal use I don't notice any speed difference between the two. When run side by side, the V5 is faster opening ebooks and perhaps 25% faster turning pages. The V5 still has the black flash on all page turns.
I did not extensively test the TTS capability. See Review of Hanlin V5 (Malaysia)
for a video of TTS in English (at the bottom of the post). It is not available in MOBI or ePub. It is available for DRM-free PDF by switching from Adobe Digital Editions to XPDF. The XPDF mode is the old V3 PDF viewer (pre-ADE) and it isn't an option on the V3 with ADE. Note that even with XPDF, TTS of PDFs will depend on how the PDF was produced.
Overall, if you like your V3 a V5 is more of the same in a smaller package with refreshed hardware. Sony is certainly betting that "basic" means 5", and perhaps they are right. I would certainly recommend the V5 over the V3 for new buyers unless they clearly needed a 6" screen.