Okay, I'll compare Alola Ash and Tai from Digimon Tri.
Ash's team:
he also has all of his Z-Crystals.
Tai has only Agumon that can Digivolve up to the WarGreymon. For the sake of comparison I would put WarGreymon on 600 BTS, with Agumon probably somewhere about 380-400. Agumon is Fire-Type and gains Steel-Type once it evolves in MetalGreymon.
I should probably also put disclaimer here that I'm on up to date with the SM anime, so this might not be as accurate...
I think that Pikachu is the strongest Pokémon on Ash's team, with Lycanroc closely behind, then Torracat and then Rowlet. I would say Rowlet is weaker that Agumon. It wouldn't do much to it. Torracat is probably on the same level as Agumon, but isn't really effective type-wise. Lycanroc could beat Agumon without any problem and would probably be at the same power level as Greymon. Thanks to its type advantage it probably do some serious damage that could be fatal in the 4 vs 1 battle. Depending on the situation, Greymon might have the need to evolve into MetalGreymon, which would mean victory against Lycanroc. As for Pikachu, I would say it's on the same level as MetalGreymon, but it wouldn't do much because of its size and attacks. Quick Attack and Iron Tail are useless. Its Static ability could be useful. But once MetalGreymon evolves into WarGreymon, I don't think Pikachu would do much without any help from the previous battles.
Now let's simulate the fight. Ash starts with Rowlet and Tai with Agumon. If Tai is determinate to win, he would immediately evolve Agumon into the WarGreymon. This would mean that Rowlet won't do any damage at all and faints with the 1st attack. Next up is Torracat. Once again, this would be quick battle. Lycanroc's Accelrock and Counter could do some serious damage to the WarGreymon (given that WarGreymon is much more faster, I don't think that Stone Edge or Rock Throw would ever land), but in the end, it would really just be a matter of time before loosing. Last up is Pikachu. I already mentioned that it wouldn't do much, but it could paralyze WarGreymon and depending on how much is WarGreymon tired from the previous battles, one critical Z-Move could be fatal, but that is many ifs and as I said earlier, the only Pokémon that could do damage to it prior Pikachu is Lycanroc. And WarGreymon has Terra Force, which is pretty much Hyper Beam without the negative effect.
So in the end, I would say that Tai wins in the 95 %. 4 % is for the case when Tai is unlucky and Agumon gets hit many times to the point that it faints at the end of the battle with Pikachu, which would mean the battle would end in draw. The last % is for the situation when Ash is extremely lucky, all his hits are crits and his Pokémon dodge every single attack and win in the end.
I might do Kalos Ash vs Tri Tai later, because I feel like it would be much more interesting with fully evolved team and Battle Bond Greninja on Ash's team. I would say that it would be much closer battle.
