Knipex makes a wide range of 115-125mm side cutters, certainly not the only quality maker but they have a solid selection and good info on their website.
Model lines 62, 64 are small end and angle cutters 70, 75, 76, 77, 77H, 78, 79 are small side cutters 72 is for plastic; 75, 77, 79 are the top end, 77H is twice the price, 78 is half the price, 70/76 are mid grade. Online prices vary widely with individual sub models at the high end.
The variables in general are.
- Joint. Riveted lap(the cheap line), forged integral lap aka single joint(look similar to box, mid range line), Box(one side passes through the other and are riveted, high end of line), and bolted(adjustable, high end of line)
- Bevel angles, fine angles make cleaner cuts on soft materials but are weak, steeper or more balanced(left/right) edges are used on harder materials. Thus true flush side cutters generally don't last as long, especially cutting steel and center cutters are used on large two handed bolt cutters.
- Steel hardness is directly proportional to strength for all common steels.(However toughness or impact energy absorption and abrasion resistance can vary widely at a given hardness)
Hardness Rockwell C is popular for hardened steel but vickers covers a wider range of materials. Steel above about HRC 60 lacks any noticeable ductility and will fail by chipping rather than mushing.(either way the edge is ruined) Maximum hardness of any tool steel is 65-66HRC**, cemented carbides and ceramics can be over 85. Common stainless kitchen knives are often 56-58HRC Japanese plain-steel are 61-64; tempered hardware screws, springs and such 30-50HRC copper and very mild steel is below HRC-0.
Rough conversion to Vickers hardness(Below 200, vickers is roughly=brinell): HRC65=HV700, 50=HV500, 30=HV280 10=HV180, mild steel is HV100-220, hard drawn copper HV90 annealed copper HV50, aluminum 6061 HV30-HV140.
Knipex makes cutters with edges ranging from HRC 56 to HRC 64, a line with carbide HRC 81 (77H), and a line for plastic(hardness not listed). Why they make the softer items is probably just expense of manufacturing, except the stainless model where it is likely metallurgical and raw material cost. I suppose in certain clean areas, like around food, it would be better to bend then to have steel chips. - Nose shape, this is mostly just preference although the slimmest tips will be a bit weaker and more flexible, the heaviest rounded noses may not fit in small spaces, short heads are stiffer for the same width while long heads have reach and capacity.
- Comfort: weight, handle padding bulk, spring open or no spring, when clamped do the handles pinch together or is there a space for skin.
**HRC 65-66 is the hardness of pure quenched and untempered high-carbon steel martensite, it is possible for macro tests to indicate up to hrc70 on some steels(with very rare alloys used by some custom knife makers) but this is caused by a large number of carbide particles spreading out the force of the indenter kind of like gravel in concrete, the base steel matrix binding it all together is still at or below HRC66 when micro tested between the carbide particles.