Laser - I, also, have not heard either speaker, but can provide a broad outline. As time progressed, each model line (1,2,3, etc.) benefited from accumulating knowledge and solutions. So, in some ways, the latest speaker was the greatest due to benefiting from newly developed technologies, usually in higher-numbered series. The 3.6 is 1993; its tweeter is from the 1988 CS5, and the other drivers are then-state-of-the-art Thiel designs. A 1996 midrange XO change smoothed out the upper midrange. Considered an all-time great. The 2.4 is 2003; its tweeter is from the 7.2 with double-cone coincident coax ideas from the 7s. So, even though the 2.4 is for smaller rooms with less bass capability, it possesses more advanced technological solutions than the 3.6. The 2.4 is an audiophile darling.
If your room is large, you like deep, loud bass and can sit farther away (at least 8'), the the 3.6 might suit you better. If smaller space, closer position and with more delicacy, the the 2.4 might do better. By the way, they are both on the hot-rod upgrade list for future upgradibility. Beetle and Holco have tricked out their 2.4s. Note that the 3.6 has relatively less room for improvement than the 2.4. The 3.6 stock parts quality is higher.
I hope I haven't buried you in TMI. Context sometimes helps some people wade through complex comparisons. There is no substitute for your own ears, if you can arrange to hear them both.
If your room is large, you like deep, loud bass and can sit farther away (at least 8'), the the 3.6 might suit you better. If smaller space, closer position and with more delicacy, the the 2.4 might do better. By the way, they are both on the hot-rod upgrade list for future upgradibility. Beetle and Holco have tricked out their 2.4s. Note that the 3.6 has relatively less room for improvement than the 2.4. The 3.6 stock parts quality is higher.
I hope I haven't buried you in TMI. Context sometimes helps some people wade through complex comparisons. There is no substitute for your own ears, if you can arrange to hear them both.