The current state of Bitcoin L2's security budget.

The Bitcoin L1 network is very decentralized and has a massive amount of hash rate, which correlates to a very high cost to attack the network.

Let's look at the current state of Bitcoin L2s and see how secure they are from a cost view.

Rootstock: Currently secured by 48% of the Bitcoin hash rate. This is very strong. The chain is currently securing around $120m in value. One caveat here is it's not clear how many miners/pools are part of this %. It could be 2 big pools which is centralized*.

Stacks: Currently averaging 5-10 active miners spending around $50k per day in BTC to mine (and earning $95k in value). The chain is currently securing $370m in value ($340m in stacked STX, and $30m in other assets). One caveat is the network is currently experiencing an MEV issue which might affect mining incentives, which should be fixed in the Nakamoto upgrade.

Liquid: Secured by 15 entity federation in an 11-15 multi-sig. This is centralized (and capped) but the trust model is known. I haven't heard of any foul play by the federation. Currently securing $115m in BTC, It's hard to find other asset data for the chain.

Lightning: There's minimal risk if you run your own node. Options for this are getting easier. Main risk is if you use a custodial wallet solution (current estimates are 8x more people are using custodial solutions than non-custodial) It's hard to get good data for Lightning but it's overall seen as safe from a security POV.
Currently $200m in value is on the network.

Overall this gives a view of the different experiments being run to create a quality and safe Bitcoin L2.

At this point in 2023, the design space is still wide open with no clear winner.