I had a 707 before the Force, and in my case I should have just gone straight for the Force. It does everything I need it to, and I prefer working with it.
The 707’s main advantages for me are hardware-related - you’ve got more tactile control with the per-channel knobs and faders, and you’ve got more onboard i/o flexibility. You can use the macros mode on the Force to replicate some of the control features, but the immediacy of the 707’s controls always remains useful. The Force does have the potentially huge advantage of allowing you to create your own custom marco controls, which is great for jamming and improvising if you have the time and patience to set it all up.
The i/o is addressed, I suppose, by the Force’s new USB features, but that requires you to have the additional and appropriate hardware.
Sound is subjective, but I’d say both are more than capable of generating any sound you might want. The 707 is fiddlier in some ways - it’s well laid out, but you will be menu diving to some degree. But you benefit from a consistent interface, which some might prefer. The Force gives you much better control with the touchscreen, knobs and VST-style plugins, but they all have different approaches and layouts. As with most other factors, it all depends on your preference. The 707 is quite old school at heart - it feels a bit like using a rack sampler at times, but in a good way - a robust, focused system that’s fast once you’re used to it, whereas on the Force it’s not unusual to find your finger hovering over the screen while you try to remember where it needs to be. I still get on better with the Force’s approach overall, but the 707 certainly has its strengths there.
Sampling, I’d say the Force wins hands down there, unless you’re not a fan of touchscreens (in which case you should probably be looking elsewhere). The 707 is a bit more imemdiate in terms of layering samples and synths, but this is another area where the lack of immediacy on the Force is balanced by a wealth of possibilities. Streaming samples from disk on the Force is a huge advantage if it’s important to you, and if large/long samples are something you’re likely to use, it definitely has you covered.
Sequencing is an interesting category - the Force has a very robust linear sequencer (and arranger), but isn’t partcularly interested in experimental approaches in the same way as, say, and Elektron device. There are some elements and workarounds, for sure, but it’s not the same. The 707 is a bit more accommodating there, but the implementation often feels clunky. The grid arrangement on the 707 is really interesting, though, if you like working with multiple sequences and tracks in a generative or unpredictable way. Neither of them match the Elektrons for immediate experimentation, but both have tools for exploring that side of things. The arranger mode on the Force, if it’s something you’re interested in, is very nice.
When it’s all put together, I just find the Force easier, faster and more enjoyable to work with. I like to tinker around, swap things around, try out different effect chains and so on, and the Force offers rewarding ways to do all that. I think its macro system is very much an underrated gem. I do like the physical elements of the 707, and it works really well as a kind of Roland museum, but it’s just hard to go back to it after the Force. If I had to choose one, I wouldn’t hesitate to lose the 707. That sounds harsh, which is a shame because it’s a powerful and flexible device that would have blown my mind ten years ago - but that’s how it is.
(If the choice was Force or Octatrack, then I’d have a problem on my hands - which is another testament to the Force.)