Here is my analysis, you are in a large urban house, walled, with guards. Despite that, the guards are dead and at least two attackers remain, possibly as many as five.
That means they didn't come with water pistols or pointy sticks. They are likely adequately armed and prepared.
You mention you can't carry a bunch of mags. So we need to maximize both your onboard ammo capacity and the effectiveness of each round.
The MP5 and Saiga are immediately out because both of these are less suitable to your situation. The MP5 packs the same ammo (or less) as your other choices; but is less effective per round and with the stock extended it isn't all that much shorter or handier than your other choices either.
The Saiga is plenty effective (assuming no body armor); but you've already said you can't carry extra mags and 8 rounds is way too few for multiple attackers who have just breached a wall and eliminated multiple guards.
That leaves the four rifles. Of those, penetration concerns can be addressed by ammunition based on whatever type of structure you live in. If you have to go with ball ammo and your building materials are similar to American homes, then it may be worth giving 5.56 a thought.
Otherwise, I would pick the firearm that you are most proficient with, most confident in, and have the most training with and make sure it has sights you can use at night. A zero magnification red dot sight is probably the best for this. A weaponlight is pretty much a must too; but if you can't get the training on how to use it, it may not do you much good.