I removed a shower from my small bathroom and now need to cut the cast iron drain pipe down to as close as I can to floor level. I'm not sure whether a sawzall or an angle grinder is best to use in this situation. If a sawzall, what blade would work? Thanks!

Teresa

It is a chain with hard wheels on the links that goes around the pipe and scores the surface.
The cast iron is then snapped off on the score line.

Sewer gas is flammable, so tolls that produce sparks (angle grinder) or can result in heating the material in the cut (sawzall) are not recommended unless the pipe is no longer connected to a sewer system.
As long as it is connected to a system it can have flammable gases present in the pipe.

You do need to be sure it is iron pipe and not galvanized steel pipe.

Iron pipe was not used all that much in size below 3 inches.

Old iron pipe has belled ends (AKA 'hubs') with joints caulked (oakum) and topped with lead (the lead is poured over the caulk and then used to compress the caulk to create the seal).

Some newer iron pipe has no hubs and uses metal jacketed elastomeric clamps to join section (called 'no hub').

Galvanized steel can be cut wit a typical 'pipe cutter' with a hardened wheel.

If so, the easiest method is to go under the floor and cut the line back a couple feet using s chain snap cutter to cut the cast, the use a Fernco to conect either PVC or ABS and install a new closet bend up to the bathroom