I have two Subtronic pro 160 and 2 Hartenberger 250. For travels, the Hartenbergers are by far too heavy: Over water, one of them is heavier than both Subtronics. Furthermore, in manual mode even the -5 setting of the Hartenberger is often by far too strong. Advantage of the hartenberger: it is very probable that you will not need any support. They just do their job. Furthermore, they have pilot lights that are usable, the ones from Subtronic do not deserve the term "light", it is just one single weak LED, their intensity are equal to half a candle light.
Hartenbergers are +- neutral under water, but still bulky (I would not like to dive with 2 of them in strong current).
Regarding size, the Subtronic Nova (270) is in between the Subtronic 160 and the Hartenberger 250. I think there is absolutely no reason to take the Hartenberger 625. It is, furthermore, not even fast enough for preflahes and you would have to work in manual mode only. With a TTL converter, you can use the Subtronics or the Hartenberger 250 in TTL mode which works perfectly for macro (reduce the fash intensity in camera settins when using Hartenberger in TTL mode sine the TTL converter I own is made for weaker flashes). The Subtronics are a pain in the ass during night dives in manual mode because you cannot read the back Panel du to lack of light there. Hartenberger works great, the buttons have a built-in light.
Although Subtronic claims 116 degrees light angle and Hartenberger only 90, they are absolutely comparable. But as mentioned, the Hartenberger is much stronger, and the difference is for sure more than 160 vs 250 Ws. Therefore, either the Subtronic has less than 160 Ws or the Hartenberger has more than 250 Ws.
Advantages on both sides, it absolutely depends on your needs which flash works best for you.
Hope this helps a bit.
Jens