The solid state contactors are a good idea for your starter, where it is intermittent use and high-surge.  They ought never to go bad, leaving you stranded on a cross country.  Aircraft Spruce sells some suitable for your starter.

With low surge at turnon the mechanical relays are a better choice.  In addition to the wasted energy turning into heat, solid state relays may "leak" power even when "off," allowing your battery to drain over time.


Best regards,

Bill Reister