Do you need to ride gentler with a dynamo hub? I am going to purchase a dynamo hub and the way I like to ride is carefree abandon - going offroad, up and down curbs, straight through potholes, etc. My bike is a 90's rigid mtb with road tyres (26"). 

I like to do pretty much everything on this one bike and want the convenience of dyno lighting as well, will I have to be more gentle with a dynamo hub because it has delicate electrics?

I only found one thread elsewhere from some people who suggested that the SON Delux would be the best choice for rough riding: http://forum.cyclinguk.org/viewtopic.php?t=18685

However, the two I am looking at are Shimano's 3n80 and Shutter Precision's PV-8, which are not quite as well built.
I have never owned the cheap and nasty dyno hubs you're looking at as alternatives, only the SON hub. 

My experience of the SON is that it has not been necessary to ride gently, and observation of other owners suggests they don't do that either. I've owned mine for more than 10 years, and done enough distance that I felt it necessary to have the bearings replaced. I've toured on it and used it on load bikes as well as commuted, and the touring was done on short wheelbase recumbents where more than half the weight is on the front wheel. Suspension doesn't matter much because the hub isn't suspended.

I managed to break a spoke in a 36 spoke, ISO 406 wheel with a deep section rim, and I have no idea how that happened... but the hub was fine.

My issues have been more with the wiring, those silly push-through plugs don't work for me, as someone else mentioned in this answer to "Pedal-powered head/tail lights". They work ok, in good conditions, but when they fail it's impossible to fix on the side of the road. And they do fail, eventually. So I have soldered better connectors on, and I use much thicker wires with heat shrink at key points. I'd rather carry 50 grams of extra cable and plug, but have lights that work for 20,000km or more without servicing, than shave a few grams and have lights that "usually work". I didn't pay the price of a hub dynamo to get "usually works".



Edit in response to question in comments: In my experience the hubs don't fail - it's not just that my one hasn't failed, it's that the bike shop that services it said that a car crash was the only time they'd seen one fail, other than the stories of people who open them up and wreck them. Don't do that.

By "usually work" I mean in the broader sense of "over the next five years". Having to sit down every year and cut the end off the cable, put on new heat shrink, re-strip the ends and re-install it... that's annoying. But it's better than having to do that at some random point during the year, on the side of the road. By "usually work" I mean the latter... you buy it, it works 100% until randomly it stops. Or becomes intermittent. That's not acceptable. I don't care if I'm riding in half a metre of seawater, I want my lights to work (I have done this and they did - some Australian bike paths don't deal well with flooding). 

My approach was to look at the connectors, and the wire, and decide that I did not like them. So I put better ones on. They cost probably 10x as much as the supplied ones, but they work. And the soldered, heat-shrink-covered join on the old connectors seems to work too.