Personally, the way I see it, Tatum is the best asset out of all the available ones between Boston and LAL (unless you start counting the stars like Kyrie, Lebron, etc. but they obviously aren't getting dealt).
Then it's Kuzma. After that, there's a solid gap between the 2nd best and 3rd, but I'd say Ingram is better than Brown, but only marginally. Then after that, it's Brown, then Ball, and then Hart.
But if you include the picks both teams could have available, Boston beats LA by a big margin. Sure, the Kings Pick isn't landing #2 or Top-5, but it still is likely a lottery pick. The Grizzlies pick, I agree with @celticsclay, that pick is looking a lot more valuable now and teams could be eyeing it down the road (including the Pelicans). They see the situation in Memphis too.
So my ranking between Celtics and Lakers assets:
1. Tatum
2. Kuzma
3. Memphis Pick
4. Ingram
5. Brown
6. Ball
7. Kings Pick
8. Hart
9. Williams (Timelord!)
10. Pretty much everything else (own picks likely in the 20s)
Feel free to argue or discuss as you please.
Two quick things, it might be unfair to Lonzo's talent, but he does come with baggage due to his dad and family. I don't think Pelicans fans will like it if they trade Davis in a package featured by Lonzo and his dad throws a tantrum about it (also directed at the Pelicans and their fans). Either way you could swap Lonzo and Brown in that mini-ranking if you want, but it's not a large gap between the two either. Second, the Kings Pick is 7th here assuming it lands in the 12-14 range, but if it ends up around 7-10, then even that could move up a spot or two here. If we hit the jackpot in the lottery and it's Top-5 (and not #1), then obviously it's 4th best here.
Either way, if LAL offers Ingram, Hart, Kuzma, Ball (all of them) then @Moranis is correct, we HAVE to trade Tatum to acquire him, and probably also include someone like Williams too (along w/salary and whatever picks). We probably have to trade Tatum anyways to acquire him (sadly) unless Brown starts lighting it up from here on out (upping his trade value), but if it's Tatum, and just 1-2 more players needed + picks, we're still in a good spot and we also aren't decimating our roster (unless that other player turns out to be Kyrie in some form but I doubt it).