Clear Rockwool, so you can see where the roots are? LOL
Clones are easy, though I find them to be the most difficult part of the whole process. Did I do them right? Are they rooted yet? The best medium is what you know and work well with (probably the first one you use).
I've always seeded in rockwool, but don't prefer it for cloning, ready rooters or pete pellets (I've only used pete pellets because they came with a couple different domes and they work, so if I run out of ready rooters I use pete until I run out. I did an experiment with Pete pellets, you can read below.
Tools: 2ft 2bulb T5 light, 2 clear plastic shoebox containers ($1.25 each Subcool's method) clay pellets, Superthrive, ph 6.0 water, scissors and razor blade
My last run was an experiment, I took clones using pete pellets, ph'd 6.0 water and a little dab of Superthrive, that's all. took 12 days for the first to show root, 20 days before I transplanted the last one, a SSH that was still now showing roots, but looking so healthy and I needed the space. A sick Purple Trainwreck plant I actually pitched right after cloning it, I was able to take 1 cut and it seems to be doing ok in soilless.
The larger cuttings had burned/dying tips of the top leaves, I'm sure due to not using a cloning gel or other cloning product, I thought I was losing them but I let em go and they rooted. I wouldn't recommend doing it this way but if you had to you could