We have installed two flatpack Ikea kitchen cabinet sets and one flatpack kitchen cabinet set from Kitset and I have to say that Ikea's installation instructions are more detailed, if you are reliant on instructions. Ikea screw hardware is much better and more suitable than Kitsets'. Importantly, Ikea pre-drill their screw and dowel holes, which made assembly much easier than Kitset. With Kitset we had to use reference square edge on internal angles to maintain square befiore fastening. As Ikea use dowels + screws, We found this more reliable than having to use screws only on Kitset. Rear panel of Kitset cabinets is 16mm chipboard vs. 3mm mdf on Ikea, so arguably they could be structurally stronger, except they dont allow for securing the back panel to the base panel, a big oversight which we had to correct. But after installing Ikea units, there's no real problem, key is to secure them (and kitset)to studs in walls if heavy items are loaded in them.
Kitset claim to use HMR chipboard, and will not warrant for outside use even if totally undercover. With both, we prefer to use a DWD intergrain sealer to mitigate/delay moisture entry into panel (sawn) end grain, but this will cause minor end grain swelling which you'll need to lightly rub back to maintain tight it assembly.
Kitset have flexibility to make custom sizes - Ikea no way, made in china/offshore. Summary: if you want it now and can work with standard sizes, then Ikea. If you can wait for your order and want HMR/stronger back panel then Kitset. Check your pricing...p.s. Bunnings cabinet finish is ordinary IMHO, and not necessarily cheapest option..check hinge/runner quality.
