If the car has spare wheel well deep enough to take a full sized spare I see little advantage in a space saver and some disadvantages. You might save a couple of kilos weight, and a few mm less depth, But any gain in storage space is under the boot floor, and may be quite minimal as you can store quite a lot more stuff inside the hub of a full sized wheel than a spacesaver.
Space savers can be quite expensive. Even second hand ones which may need a new tyre due to age deterioration. New spacesaver tyres are comparatively expensive. Some spacesaver 'specialists' sell stock that is not brand new, but taken from another car. Maybe never used, and they might have replaced the tyre.
Spacesavers are speed restricted,for safety reasons and by law. Very much a get you slowly home/to tyre fitters in an emergency . With a full sized spare with a good tyre of the correct size you can complete your journey at full speed , and take more time finding a good deal on puncture repair, or a replacment tyre of your choice. Less chance of being ripped off on price or having to settle for whatever tyre they currently have in stock.
Plenty of full sized wheels available from car breakers etc which should cheaper than a spacesaver even if you need to replace the tyre . (beware ,even if its an 'unused spare' the tyre may need replacing due to its age . It may be better to buy a good wheel cheaply,because its tyre is rubbish and replace this, rather than pay extra because the tyre looks ok but may not be.
