There are basically 3 types of broad-band microwave splitter/combiners: Wilkinson, Reactive (Air-Line) and Hybrid.
Wilkinson: Generally low-cost micro-strip devices which offer good performance characteristics for both splitting and combining at lower power levels. Wilkinson splitters typically provide 20 dB of isolation at the output ports (as splitters, or input ports as combiners.)  The insertion loss is higher than that for reactive splitters or hybrid couplers and they are not highly rated for PIM performance. A popular series is the Dx-77FN.
Reactive (Airline): Low-cost, high performance splitters.  Lowest loss and superior PIM performance as a splitter used in the most loss sensitive locations.  Not recommended for power combining applications due to the lack of internal resistor elements and poor isolation characteristics.  The Dx-55FN and Dx-88FD are popular reactive models.
Hybrid: Highest cost but best overall performance.  Superior isolation characteristics are especially desirable in power combining applications. Also suitable for high powers where the external termination keeps the dissipated heat away from the circuitry.  The CA-84FN is frequently used in such situations.