Recently, the combination of cooperative communication, Space-Time-Frequency Codes (STFCs) and Multiband OFDM Ultra-Wideband (MB-OFDM UWB) has been proposed to improve the data rate, system capacity and reliability. This paper provides insightful performance evaluation for our previous proposed cooperative communication schemes for MBOFDM UWB systems. In particular, this paper shows that the usefulness of cooperative communication schemes is decided by the mutual relation between the signal-to-noise ratio (SNR) of the inter-node links, referred to as inter-node SNR, and that of the uplinks, which is referred to as uplink SNR. For a certain uplink SNR value, cooperative communication becomes useful when the inter-node SNR is above a certain threshold, the so-called cooperative SNR value, and vice versa. The cooperative SNR values corresponding to different uplink conditions have been derived from the simulation results for the UWB channel models CM1 and CM2 for illustration. Two important observations drawn from this paper are that, in some cases, cooperative communication for MB-OFDM UWB might be still beneficial even when the inter-node links are relatively noisy, and/or when the source nodes are located further apart from each other than from the destination node; and this benefit over a non-cooperative counterpart is more significant when the uplink channels are more dispersive.