Size or compactness of the spectrometer is dictated by geometry, and cooling electronics. Speed is governed by pre (onboard) or post processing (USB/ embedded or external PC). We provide an onboard processing option. Sensitivity is important if you have very little light from collected from your sample. A low f/# spectrometer should be considered with the option of double pass geometry, larger slit size, and high QE detector. Signal in SNR is dictated by the illumination power of the broadband or laser source, wavelength chosen for Raman and Fluorescence, light collection (low f/#), and the QE efficiency of the detector. Absorption and transmission spectroscopy methods are typically are not light starved, while light collected from the sample tends to be more of an issue with reflective, scattering (Raman) and fluorescence spectroscopy.  The noise in SNR is reduce by cooling, averaging, reduction of stray light, minimizing read noise, and having a high QE detector.