Having thrown them both, I would hazard a guess that the Fanatic BTU is quite close to the Lightning, but not at the Lightning's stock 320 grit, which was an insane starting point even back them. Remember that the while the BTU's name is "Better Than Urethane", it is NOT urethane, but resin. It's been many years since I've throw a Lightning; so take this with a grin of salt.
Although I haven't thrown one, I would also suspect that the 900Global X is also very close in overall concept to the Lightning (low-ish RG, low differential, dull coverstock). I think it is probably a tad stronger, but with today's oil, that is not a bad thing.
https://www.buddiesproshop.com/shop/900-global-x-bowling-ball-6071/