I've had an original Sigma 70-200 APO for 10 yrs and it's a cracker on the K-3/K3 II with very fast AF and great IQ (and no HSM issues, cause it doesn't have HSM!). OTOH, I've also got the 55-300 PLM and that's much lighter and great
until it loses AF lock (and it has a much smaller max aperture)!
On balance, the original Sigma 70-200 APO has better IQ but it's a very old lens and spares may be difficult to obtain if fails (although my used one never has in those 10 yrs), whereas the PLM is lighter and very good but a much smaller aperture and has only limited reliability history.
Also, if you set the body to AF and the lens to Manual, then the Sigma has "quickshift" like many Pentax lenses.
One other factor to consider is that the manual focus ring on the Tamron (and of course the PLM) rotates in the same direction as Pentax lenses, whereas on Sigma lenses the ring turns in the opposite direction - and that can be very confusing (except not for me as most of my lenses are Sigma
)!