I have owned quite a few cases over the years, so here's my take:
Instroke Premier Line (old Germany factory) 1x2 (2) 2x3 (1): These cases were simply a best bang for your buck case...the vinyl was a heavy heavy upholstery-grade that looked just like leather, with the famous Instroke interior...just a great all around case...damn near bullet-proof. Cues load either way, and longer cues would fit. Nice long storage pocket. The newer Instroke Premier cases do not appear to use the same heavy duty vinyl as the old cases did.
Porper 1x2: Case was well made with a lighter grade vinyl, tube interior. Cues must be loaded in a certain way to fit. Would not accommodate longer cues easily. Didn't care for the 'rattle' of the cue inside the case when carried. Pocket too small. Reasonably priced.
Guiseppe 1x2: My review would be very similar to that of the Porper.
Ron Thomas 2x4: This case is similar in construction to the It's George, GTF Prestige and Centennial cases. That being the case shell is an extruded oblong PVC tube with a sleeved interior. Cues must be loaded in a certain order, but do not move around or 'rattle'. Case was well crafted. My main 'complaint' would be that in many cases the leather used is a bit thinner, and some of it can be prone to nicks and tears.
Murnak 1x2: Case was well made, using a nice heavier weight leather, quality fittings, that was then hand-dyed in red, then over-dyed in black, producing this wonderful black cherry color. Mine actually had a pocket on it, but it kinda stuck outside the lines of the case itself, making it easy to catch on things...and it was small. My main 'complaint' about this case was that my cue really rattled around inside the tubes...which worried me a bit. No doubt the case would last a lifetime.
Engles 1x2: Construction like the Fellini, Gore, and GTF Replica cases. Used very thick leather on the exterior, and a sleeved interior. Cues need to load a certain way, but do not move or 'rattle' around. Back seam not as clean, typically, as that found on the Thomas cases, but the leather was much thicker, making it a little tougher to do. Well made, with no two every actually being alike. These are no longer being made, and since I need a 1x2 for solo carry occasionally, I opted to keep this case, because I really like it....preferring the folded leather ends over the wood/plastic ends.
Sterling Wave 2x5/3x4: From the creator of the original Instroke case, comes the newest bang for your buck case. Reasonably priced for just about everyone, these cases feature either a vinyl/faux leather exterior, or a nylon exterior. Nice large pockets, self-healing zippers, comfy carry handle, and backpack style straps. But it's what is going on inside that makes this case so great for your cues. It's called the Ultra-Pad Interior...with what is called 'Organic Rebound'. The interior is super plushy for your cues. While the interior appears to be sleeved, there are actually tubes inside for maximum cue protection. You can turn the case upside down, and your cues are not coming out. When you open the case lid, the cues will most times, pop right up for easy retrieval...no digging down inside the tube to get at it. If they don't pop up right off, a quick little upward shake and there they are! The 2x5/3x4 interior allows you to carry 2 butts, 5 shafts or 3 butts, 4 shafts...which I think is brilliant. Gives you a little bit of versatility in carry options. All in a footprint slightly less than a typical 2x4 case.
I have not had experience with Whitten cases. They are visually very nice cases, but my concern is that garment leather is often used, and it may not be a great every day carry option if you wish the case to remain nick or tear-free. Also, again, tube interiors, which bring the 'rattling' issues back.
I also have not had any experience with Justis cases. They have a great following, and are well made. Most recent cases feature a sleeved interior now over the older tubed interiors, making them lighter than before. Top quality leather and fittings are used. They also tend to retain their value, and re-selling them easily is generally not an issue. It is my understanding from a recent post that Mr Justis made, that he is not accepting orders at this time.
Lastly....if you like the interiors of the Sterling Wave cases, but want something in leather, then you can go directly to the source and order yourself a JB Case. If you can dream it, he can very likely build it. He can also do the Wave type cases, but in a different exterior style, using canvases, nylons, or a heavier grade vinyl.
On a smaller scale, there is also Rusty Melton, Marc Turcasso, and Rex Goulet....all doing some really top shelf, high end tooled leather cases.
Hope this helps!!
Lisa