Bert is better but positional scarcity benefits Mantha in the trade market.
Let’s ignore the vax issue (which I honestly am not sure that you can), if Im building a team then I’d take Bert over Toffoli. If im a playoff contender looking for a top 6 winger, I’m taking Toffoli everyday over Bert. The guy has scored big time goals in the playoffs over a number of years and that is invaluable. There’s no coulds or shoulds about how he will respond to playoff hockey.