Monrad is right. Tamiya is about your best bet for a Tiger. They have early, late and mid variants... Academys are good... Italeri isn't horrible but overall Tamiya is the easiest to build by far.
Pz's As stated above... depends on the model. I prefer DML kits over Tamiya because of the indi links. You would need to pic a version before choosing a manuf.
Shermans, DML does some good ones but the tracks usually scare armor newbies away. Tamiya's newer Shermans are nice and easy to build. The fit is usually near perfect...
Whatever you choose good luck...and glad to have another prophead fading away...