It depends on what you are looking for. Sonsub are a big company lots of vessels lots of ROV’s. Hallin are an emerging company with off the top of my head around 6 workclass and a hand full of eyeballs. They get a lot of work outside of the North sea which is good but then again so do Sonsub.
From experience of both companies I find Hallin treat you as a person with a bit of respect and listen to your opinion where as due to the size of the company you are a bit of a number at Sonsub.
The thing with ROV companies is whether the contract conditions suit do you want a salary with fixed pay or a day rate.
Also consider where you will advance the quickest and what type of work you want to be involved in. Where have you come from I guess with OI probably drill support. Moving onto to Sonsub where you are suddenly involved in serious construction work might not suit your experience where as Hallin tend to have a lot of pipelay/inspection and survey work which might be a more appropriate step in your career development.
Both companies have good and bad points so the contract wording and pay has to be the basis for the decision not peoples opinion on a forum where there are some very bitter and twisted old souls around.
My personal opinion of Sonsub is very negative as with Steve Bell I really liked Hallin (Hi Steve) it is a big decision to make but at any time with any company you are only a month away from leaving if you do not like it.
I would be cautious though about working for other firms agency whilst still under contract you could easily get burnt doing that.
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