Maybe a not-quite-so-simple question (broader in overall scope than it might seem
).
Browse among the "pocket pistol" threads. Also look at the threads discussing the various subcompact pistols (chambered in "service calibers"), too.
Ankle carry involves some arguable pro's & con's.
Presuming you can get around the "brick on the ankle" effect, and find an ankle holster which suits
your perceived needs, activities, ankle, pants legs, etc ... there's the access & usage considerations.
An ankle holster puts the weapon as far from your hands as it's possible to get. This means reaching farther. It also makes it nigh unto impossible to provide retention against unauthorized access.
Yes, it can be handy for use while seated (especially behind the wheel), but it can also make it more accessible to an attacker (especially in some circumstances if you find yourself on the ground).
If you've become accustomed to clearing everyday obstacles with your ankle (walking, climbing, running, slipping by something, etc), it can change things (that "ankle gun lump) can start hitting against things your ankle formerly "cleared").
I've seen my fair share of both uniformed and plainclothes cops unknowingly expose their ankle-holstered weapons in public, mostly while seated in restaurants and coffee shops, but also in other settings.
Practicing to access, draw & present an ankle-holstered weapon reasonably requires some training, practice and adjustment. Hard to do if you're trying to "get distance" away from an immediate threat, for example.
Guns carried on ankles are generally more easily & often exposed to environmental elements & contaminants.
Some folks like the Centennial-style J-frames ... some like itty bitty "sub-caliber" pistols ... and some like to carry guns on their ankles that many folks normally carry in belt holsters.
Whatever is chosen, for whatever reason(s), in what ever caliber/make/model ... and however the owner is trained & practiced to access it, when needed ... the owner still ought to be able to shoot it safely, accurately, controllably & effectively.
These are some of the thoughts I suggest folks consider when they come to me and ask about choosing a weapon for ankle carry.
Good luck in your research.