The reason I recommended the FT02 Silverstone case is because it is similar to the Lian-Li PC-7FNWX but has no front intake fan, and actually uses a stacked air effect. (Air is brought from bottom, exhausted at top.
The quality of the case is superb, cooling is superior to both, and keeps a very elegant look to it.
Between the Obsidian 800D and the Lian-Li PC-7FNWX I'd say choose whatever you feel more comfortable with. Both's cooling solutions are similar, with the Obsidian of course taking the lead. Both should not be considered for air cooling enthusiasts.
I will elaborate more on what JohnnyLucky mentioned:
* It is the same design as the Dragonlord k62 on the inside, the difference is there is no plastic bezels on the outside, it has a more polished surface look and does not have a full front panel ventilation. And finally the top ventilation plastic bezel was removed, and so where the ventilation holes for additional top mounted exhaust fans.
* Has limited cooling with only 3 fans. One front 140mm fan intake, one 120mm exhaust, and lastly the power supply fan which can or may not have an impact on the case depending on the side you face the power supply. (It can act as an exhaust which is not recommended, or act as nothing when facing down.
The Obsidian 800D is widely mod-friendly, however it's air cooling is limited but still superior to the Lian-Li PC-7FNWX. I would much rather keep the Obsidian 800D.