The best juice of the i7 is Hyper-Threading meaning you will have 2 threads per core resulting in a total equivalent to 8 cores. The i5 doesn't have this feature so it's parallel processing sticks to 4 cores. If you intend to use it with applications for heavy processing that support multicore, like filme editing, video, photography, not only you'll benefit from it, as some of those applications require the i7, due to it's hyper-threading feature.
If on the other hand, you'll use applications with light workload, like text processing than i5 will suffice.
I'm a film editor and I use no less than quad core i7 (due core results in lesser cores). Sometimes Xeon CPUs. I've tried with the i5 and although it runs, it's very limiting in playback, specially since 4K joined the game, so I recommend to discard anything less than i7.
Good decision on the SSD. It´s faster and much simpler than Fusion. I also recommend only to use it as System disc, just for macOS and applications. Buy an external storage, preferably a RAID, with no less than 7200 RPM and configure it to RAID 0, for maximum speed, or if it has at least 4 drives, to RAID 5, for a balance between speed and redundancy - If one of the drives fails, you're still safe and can replace it, without any loss of data.
Hope this helps.
