I know from the outside the TAR-21 and SAR-21 look similar from
the exterior but in reality it is not inside.
Here is the stripped down of a SAR-21:

and here is the stripped micro TAR-21:

Just by looking at the bolt carrier group which are totally
different, I know from a fact they are of different design, yet ppl
still want to believe SAR-21 is a copy of Tar-21!!!
As for the Bionix 25, yes ,it is cramped but that is not due to ST
fault but rather the requirement of SAF to have width within
3m.
All other modern IFV like Bradley & Warrior which is as well
armed & with good protection as the Bionix are all have width
above 3m.
Fot it's size, the Bionix it is extremely well armoured( with steel
hull & MEXAS type composite armour), so in a war , you will
rather be in a Bionix than in a M113 Ultra!!!
As for the Terrex eventhouggh SAF has yet to adopt it, it is well
designed platform with double floor & lower V shaped hull can
protect the crew from a 12kg TNT anti-tank mine blast.
At 17.5 tons with road speed up to 120km/h & swimming speed of
10km/h & a comfortable ride with suspension stroke of 400mm, it
is actually not a bad design , in fact Turkey was reported to have
selected the Terrex for their new wheeled IFV.