SSD write speed is slower than read speed but you don't have dsk access latency to pay, so will nearly always be faster than HDD, especially for Maven builds which spit out lots of small files (ie very random access)
Read this reasonable summary of the SSD vs HDD performance differences but I am confident that for every Maven build you will find it is access latency and not write throughput that affects your build speed.
TL;DR go for the SSD