Hi, I will reply with regards to sonic differences, features aside.
The LS 100 with its 6SN7 tube as basis of design is intentionally a bit on the tubey side. Not extremely so, but not entirely neutral. The 6SN7 tube has a 'fat tone' that adds body and weight to the music. The circuit design also has very low distortion and extremely good bandwidth.
The SWL 9.0SE (original) was designed around the 5687 tube, which is a very neutral tube that is faster and more detailed sounding than the 6SN7. The original SWL 9.0SE used SS components in the tube circuit (as does the LS 100), and the result was fast and revealing while still maintaining the 3D quality of tubes. Most people loved the original SWL 9.0SE, but some wanted a bit more warmth.
The SWL 9.0 Anniversary Edition uses the same 5687 tube, but in an all-tube circuit and improved power supply. The result is a delicate balance of the resolution and speed of the original 9.0SE and a touch more tube warmth, due to the lack of SS components in the circuit. The Anniversary Edition is a matter of 'less is more' in terms of circuit topology. Based on what I have learned in my recent foray into tube amp design as well as the Elyse DAC and PH 150 phono designs, there is a delicate balance achieved that is both musical and accurate.
To sum up, the SWL 9.0 Anniversary Edition is more neutral and resolving than the LS 100. If you prefer more tube warmth, the LS 100 is a great choice. If you like tubes, but want a neutral presentation, the 9.0 Anniversary Edition is the way to go.
Ultimately, the 9.0 Anniversary Edition is meant to be the ideal 'Entry Level' product into MWI. It will pair exceptionally well with tube or SS amps and with the built in headphone amp, will also drive modern headphones (except Stax type pure electrostats) well.