I would get the rigid fork. You don't really need suspension off road, just slow down some. If you only ride trails occasionally, I don't think you would be doing any extreme rock gardens or drops. I think you could find a fork cheaper than $75 though. I only paid 35 for a used Surly 1x1 fork awhile back, and I've seen generic ones on ebay for less. They aren't hard to change yourself except for knocking the bearing race off.