What tool is the best for a solid wire?


It does not matter that much what tools to use. You should choose any tool designed for work with V-shape dies, as V-shape dies are the best for crimping of solid wires. It is important to remember to choose a lug with nominals cross-section 1 or 2 points less than a cross-section of a wire.
Crimpers ПК-16 and ПК-35, however, are designed only for crimping of stranded wires regardless that they are equipped with V-shape dies. Small cross-sections can be crimped with ПКГу-50 made by KBT, but don’t forget to change the die to a V-shape type.
Anyway, before dealing with solid wires, you should decide if you need a lug at all. It is known that cables with small cross-sections can be installed in the necessary connection without a lug- they can be just bent around a screw and fixed with a washer, for example.
Power cable lugs should be crimped with the following tools made by KBT: ПМУ-120 and ПМУ-240, as well as hydraulic ПРГс-240.