It's been quite some time since I did Loch Ness Monster (6 years) but I'd go with Tennessee Tornado anyway. It has the best first drop on any Arrow coaster and still stands out against other multi-looper drops out there. The inversions are also huge, weird, and intense. I just wish it was a bit smoother.
Loch Ness Monster is smoother and quite fun but the layout isn't as strong. The drops, loops, and helix are all solid but the second lift hill draws out the pace. Tornado doesn't waste any time.
I can't really think of any other truly good Arrow loopers so I hope these two stick around for quite some time.