4.5 acres is plenty for either sheep or pigs but also depends on if it is open pasture, wooded, etc. You have water access so that is a great start.
If pasture I would go with the hair sheep. Can almost be maintenance free on pasture and very little input. Would need to consider if you’re just looking for feeder lambs to grow out and harvest in fall/winter or actually over winter a flock where you’d likely need to supplement some feed.
Pigs work wonders on wooded terrain. Cleared out about a 1/3 of an acre strip of woods for me that was all thick underbrush. When we bought our property we couldn’t walk through and now it looks plowed with the larger trees still in tact. Eventually I’ll move them out to allow for grasses to grow in.
I will say with pigs you spend a lot more on feed unless you can find a source of scraps from a friend, neighbor, restaurant, etc.
With the size of land available to you - i don’t see why you couldn’t manage both. May take some planning but could definitely be done. Would suggest starting with one though!! Hope that helps a bit.