Which is easier to solder: TSSOP or QFN?

For hand soldering I'd go with TSSOP. QFN pretty much requires hot air, whereas you might be able to get away with a soldering iron with a TSSOP. The pitch of QFN can be smaller too, which is more difficult with home-made PCBs, but TSSOP can be small too. Sometimes they have a exposed pad in the center that needs to be grounded, which makes routing more difficult.

One issue with QFN is you have to consider the package lying flat against the board without any gap under the package or between pins. This means you can't use conductive flux since you can't guarantee the flux will be rinsed away under the package. I know this because it actually happened to me. A local manufacturer that specializes in small quantity hand-built boards was new to QFN and didn't think about this. The boards we got back didn't work for various reasons. Eventually I figured out that pins were being shorted together under the package. The resistance was surpringly low, like only a few 100 Ohms in some cases. What a mess. Letting the boards sit in clean water for a few hours helped, but ultimately we had to remove all the QFN packages with our hot air station, clean the mess, then re-solder them with rosin flux. Then the boards worked as expected.

For real professionally fabbed and built boards, there is no issue with QFNs, but for do it yourself situations they can be tricky.

If you're not soldering by hand they should be equally easy to solder. Visual inspection afterwards will be easier for the TSSOP, just like putting probes on the pins during debugging.

On the other hand the QFN has the advantage that there are pins in both X and Y direction. During reflow the surface tension of the liquid solder paste will pull the IC perfectly over the pads, even if positioned a few tenths of a mm off. So the QFN will do this in the two directions, the TSSOP mainly in the length direction only.

If the QFN has a thermal pad they often advice not to apply solder paste over the full pad, but do so in a pattern of smaller dots.

That's because when heated boiling flux may cause gas cavities, which push up the IC so that pins may not properly be soldered. Reducing the amount of paste for the thermal pad avoids this.

And Always make sure when Applying the Solder at the bottom GND PAD of the QFN to keep it as small as possible so that the QFN will remain flat on the pad. That help with good solder re-flow and PINS Alignment.