Optical coherence tomography (OCT) based on spectral interferometry has recently been examined, with authors often suggesting superior performance compared with time domain approaches. The technologies have similar resolutions and the spectral techniques may currently claim faster acquisition rates. Contrary to many current opinions, their detection parameters may be inferior. The dynamic range and signal-to-noise ratio (SNR) correlate with image penetration, the contrast as a function of depth. This work examines the theoretical sensitivity, dynamic range, and SNR of the techniques, within the practical limits of optoelectronics, taking into account often ignored or misunderstood classical factors that affect performance, such as low frequency noise, analog to digital (AD) conversion losses, and methods for potentially improving sensitivity, including fast laser sweeping. The technologies are compared relative to these parameters. While Fourier domain OCT has some advantages such as signal integration, it appears unlikely that its disadvantages can ultimately be overcome for nontransparent tissue. Ultimately, time-domain (TD)-OCT appears to have the superior performance with respect to SNR and dynamic range. This may not be the case for transparent tissue of the eye. Certain positive aspects of swept source OCT leave the possibility open that its performance may approach that of (TD)-OCT in nontransparent tissue.