Degenerate birdcages were discussed by Nistler et al(1) and Alapappan et al(2). Loop arrays have been discussed by Alagappan et al(3) and Guerin et al(4), and TEM arrays by Ryu et al(5) and Tian et al(6). Instead of just doing comparative simulations, in our study we are comparing data from actual prototypes of full scale body coils and examine the real engineering issues with implementation.A 16 ch TEM array was built with a patient bore of 68 cm (fig1). The rungs were 26 mm wide, 420 mm long and had 4 capacitive junctions of about 36 pF. Distance to the RF shield was 20 mm. The 8 channel version is the 16 ch TEM with half of the rungs removed. An 8 loop array was built with a 70 cm patient bore (fig2). The loops were 525 mm long, and 340 mm wide, traces were 20 mm wide (45cm FOV at -6dB). The distance to the RF shield was 20 mm. The loops overlapped by 24 mm to minimize mutual inductance between direct neighbors. There were 9 capacitive junctions per loop. The measurements on these 3 coils were compared to a 16 rung high pass birdcage coil with a diameter of 70 cm, rung width and length of 7 and 39 cm, and endring width of 10 cm. Distance to RF shield 20 mm (45 cm FOV at -6dB). A scale model degenerate birdcage was also built with a diameter of 242mm, length 192mm. The distance to the RF shield was 14 mm. The parallel transmit coils were connected to an 8 channel transmit chain with amplifiers mounted close to the magnet (VSWR requirement<2). HFSS ( Ansys inc) finite element simulations were performed in addition to the measurements.The degenerate birdcage was found to be extremely sensitive to perturbation of symmetry e.g. roundness of coil, patient or shield, as well as alignment. The best isolation between channels that could be obtained was -9 dB, insufficient for a VSWR<2. For this reason the degenerate birdcage was not considered for full scale duplication. The following data is for 16ch TEM, 8ch TEM and 8 loop array, in that order. Measured worst case isolation between neighbors was -14, -18 and -18 dB. The -14 dB isolation was not enough to obtain a VSWR <2. The measured star artifact levels due to aliasing of signal from non linear areas of the gradient was 3.1, 3.1 and 1 (Birdcage =1). The measured efficiency in an empty coil driven in quadrature was B1+ = 0.157, 0.120 and 0.122 μT/√W (birdcage= 0.243). When the coils were loaded with a load phantom equivalent to a 75 kg patient (590mm long cylinder, 295mm ID, 345mm OD, eps=80, sigma=0.7 S/m) the efficiencies were B1+= 0.14, 0.10, and 0.10 μT/√W (Birdcage = 0.154) when driven in quadrature. TEM E fields are primarily in the Z direction. These E fields (empty) are shown in fig 3 and compared to the 8 loop array and the birdcage. Fig 4 shows the Z directed E fields for the loaded coils (45 cm diameter solid cylinder, 50 cm long of muscle tissue eps=68, sigma=0.7S/m). The 8 loop array performs the best in VSWR, B1+ drop off (star artifact) and E field. The TEM performs worst for Z directed E field and Star artifact, where the 16 channel TEM also has the worst VSWR performance. Outside the imaging volume the TEM B1+ only drops gradually, and not fast enough to prevent star artifact from the non linear areas of the gradient. TEMs can be built that have a faster drop off of B1+ as was done in (7). The drop off can even be made birdcage like by adding spoilers to the TEM, but at the expense of efficiency. The Z directed E field of the TEM impacts the common mode current and balun heating in system cables that run through the bore, as well as blocking network heating for receive array elements. Previous work has concentrated on uniformity and SAR as the criteria of choice, there are practical considerations like perturbation sensitivity, efficiency, star artifact, VSWR, and E fields that should be included when making a choice of body coil.