The SL66 is still a great camera and I´m a big fan of it. The bellow is a huge advantage if you are doing macro and portraiture. With a Hasselblad, you have to use extension tubes if you want to get closer to the subject. With the SL66, you can do this effortlessly.
The SL66 also offers an instant-return mirror, which a Hasselblad does not. However, you should have in mind that these cameras are ususally between 30 and 40 years old. I think one can compare this to an Oldtimer: It will cost a lot when in good shape and you have to have it overhauled to be happy with it. You might also want a new screen for it. Accessories will also cost a lot and are rare, as are some of the lenses, especially the 30/3,5, 40/4, 60/3,5 (ultra-rare) 120/5,6 and 500/5,6. The 150/4, 250/5,6 and 50/4 are quite common. On the other hand, you can get all of these lenses (except the 500/5,6) also in Hasselblad-mount, plus some newer designs. The SL66 also has a slow sync speed. Regarding the movements: They are rather limited with an 8° tilt. I would recommend a LF field camera like the Linhof Technika with roll film back instead.
The built and feel of the camera however are exceptional and I never stop beeing fond of it, as my nick name shows.
Best, Benjamin