Some would think this as a ridiculous comparison. How could someone compare a tablet with a phablet? However, consider this: both come with SIM calling and are priced alike. You cannot use either of them for calling. So in that regard, both the devices are bigger versions of phablets, and therefore this comparison.
Size and display
The Samsung Galaxy Note 8.0 is a full-fledged tablet with a big 8 inch screen. Obviously, it weighs 338 grams, much more than the Galaxy Mega 6.3, which weighs 199 grams. Also, the tablet measures 210.8 x 135.9 x 8 mm (height, width, thickness) against Mega 6.3's 167.6 x 88 x 8 mm. So, apart from thickness, the Note 8 is almost double the size of the Galaxy Mega 6.3.
Coming to the display, the Note 8's 8 inch display comes with 800 x 1280 pixel resolution that amounts to 189 ppi pixel density. On the other hand, the Galaxy 6.3 has 233 ppi pixel density as its display has 720 x 1280 pixel resolution. Both have TFT capacitive touchscreens.