If i am going in a CQB situation - i would Pick M4 commando before i pick Tavor because the reason that struck my mind is the design and the easy mobility of M4.
M4 is a neat design and is not much attached to the body where Tavor is a case different.
Here is Tavor:
M4 Commando.
Tavor is more like an SMG where M4 is a multi task weapon , the issue here would be handling during combat and while Maneuvering , Running , crouch etc and in my opinion M4 is Much better option.
And on what basis did you choose the winner????????????
Read the facts below from wikipedia:-
M4 Carbine=
Weight 5.9 lb (2.7 kg) empty
6.9 lb (3.1 kg) with 30 rounds
Length 33 in (838 mm) (stock extended)
29.8 in (757 mm) (stock retracted)
Barrel length 14.5 in (368 mm)
Cartridge 5.56x45mm NATO
Action Gas-operated, rotating bolt
Rate of fire 700-950 round/min cyclic [1]
Muzzle velocity 2900 feet/second or 884 meters/second [1]
Effective range 500 m (550 yd)
Feed system 30 round box magazine or other STANAG Magazines.
TAR-21=
Weight 3.27 kg (7.21 lb) (TAR-21)[1]
3.18 kg (7.0 lb) (CTAR-21)[1]
3.67 kg (8.1 lb) (STAR-21)
2.95 kg (6.5 lb) (MTAR-21)[1]
3.19 kg (7.0 lb) (TC-21)
Length 720 mm (28.3 in) (TAR-21, STAR-21)[1]
640 mm (25.2 in) (CTAR-21)[1]
590 mm (23.2 in) (MTAR-21)[1]
670 mm (26.4 in) (TC-21)
Barrel length 460 mm (18.1 in) (TAR-21, STAR-21)[1]
380 mm (15.0 in) (CTAR-21)[1]
330 mm (13.0 in) (MTAR-21)[1]
410 mm (16.1 in) (TC-21)
Cartridge 5.56x45mm NATO[1]
9x19mm Para (Optional on MTAR-21)[1]
Action Gas-operated, rotating bolt[1]
Rate of fire 750-900 rounds/min[1]
Muzzle velocity 910 m/s (2,986 ft/s) (TAR-21, STAR-21)
890 m/s (2,919.9 ft/s) (CTAR-21)
870 m/s (2,854.3 ft/s) (MTAR-21)
885 m/s (2,903.5 ft/s) (TC-21)
Effective range 550m (estimated as the M16 rifle by the ammo and the barrel)
Feed system Various STANAG magazines
Sights ITL MARS with integrated laser and IR pointer, Trijicon ACOG (STAR-21), others available
Read these and compare everything and see for yourself which is better................
Also, refer to some youtube video to know more about bull-pups.
And also check the TAR-21s compactness:-