Pandalet - In a year or so when I hope to undertake the practical course I expect to have around 1000hrs, so no, not a great deal, but perhaps more than some. I agree that without a specific job in mind, the cheaper option is probably the best to simply get the piece of paper full stop, as with low experience looking for a job in a left seat (probably offshore) role it would be unlikely to be in either type, but I would't like to overlook anything if there are benefits to doing it in a more modern aircraft.
explorer99 - you have hit the nail on the head, i'm not type rated in either aircraft at present, and with it's popularity on the rise I would rather have the 135 type rating on my license incase any multi-crew 135 left seat roles VFR or IFR became a possibility. I'm not sure whether the 135 or 355 ratings are more likely to open doors? More 355's about, but more people moving towards the 135...