Increasing loft (21-22) closes the face. If your tendency is to fade, go with 21. The 23 will reduce a draw.

I’d get the 21 least that way you can take some length off it

I'd weaken the 21. Normally, I'd say strengthen the 23 because the shaft is a little shorter than the 21, closer to your 4 iron length.
Also with the 21, you've got 4 degrees separation between hybrids to start with,which is optimal.

If you have the ability to try both then do that. They could potentially perform different for you weakened versus strengthened.

Can't believe you asked this question today. I was coming specifically to this forum to ask for opinions on the same thing. Coincidence! I'm not trying to hijack the forum, but I'll ask my question here, as well, since the answers will likely apply to both of our needs. No point in starting another post.

I play T200s, but use a customized AP3-718 4 iron, which I love and usually hit well, so I kept it in the bag when I got the T200s. However, in certain conditions, it would be nice to swap out the 4 iron for a hybrid. I want a more iron-like hybrid for this spot, so it would either be an 818H2 or a TS3. I already play an 818H1 19* as my next club up from my 4i. Which would make more sense, a 21 or 23? So nearly same question as Clayton (the OP) asked, which do you feel will be the best fit between my 19* hybrid and my T200 5i; the 1/2" longer shafted 21* set to 22*, or the shorter 23* strengthened to 22*? I realize lie angles will be slightly different from one to the other, but what other benefits, shortcomings or other concerns should be considered? For me, I will only play the hybrid as an alternate to my 4i in softer conditions. For Clayton, it seems it would be his everyday club for all conditions. Any thoughts?

FWIW, I'm a mid-single-digit index.

First go to fitter, I can't see much benefit in 2* of loft separation, it would be like having a 54* & 56* wedge?? IMO the progression would look like 19* - 40.5" (80g shaft), 23* - 39.5" (90g shaft) then 27* - 38"(standard) 5 iron with the 100+ gram iron shaft?? It is definitely worth seeing a fitter for proper blending.

Strengthening loft causes a little more fade and weakening causes more draw.