In addition to the dB loss figure, the percent of braid, and nature of the jacket material need to be considered. Contamination by the jacket will change the characteristic impedance of the cable over time. The run of the cable from the antenna to the transmitter should also be considered. These will change the impedance, and create discontinuities, causing power reflection. Pass thru watertight deck fittings should be tigtened carefully in order not to squeeze the cable.
Splices are to be avoided in the cable, particularly at the base of the mast.
The splice at the base of the mast generally consists of PL-259 conectors on the cable ends with a barrel connector between. With even the best of connectors and sealing tape there may be corrosion. Also the corrosion is not just at the connectors, but moisture will wick into the braid much further that one would imagine. Another problem with splices is the creation of discontinuities in the line which change the characteristic impedance of the line at that point and will cause some of the power to be reflected. Altho' this effect is considered negligible, losses do add up.