Cleft/whip grafting is generally easier for me. The downside is that you must match up the rootstock to scion size for cambium to match up.
Side Veneer has a lot of benefits. You can have different size rootstock & scion, positioning can be more flexible, and generally you can leave on some foliage to keep pumping energy into the rootstock. Downside is that it's a more difficult cut to make, and keeping the cambiums lined up while securing with grafting tape can be challenging.
So basically, I would use all methods, if you can match size then go for a cleft or whip depending on preference. If not, go for a side veneer.