The outputs on both harmonizers are very different. While both of the harmonizers are supplied with one XLR mic/line output, the Vocalist 4 allows you to monitor and adjust the low noise filter and automated preamp.
The 1/4" output of both harmonizers enables you to connect guitars and other digital controllers; however, the Vocalist 2 is limited to only one mono line out. The Vocalist 4 has an additional guitar pass-through and ground life switch which works as an external effects processor. A headphone jack is not available on the Vocalist 2 interface but is offered on the Vocalist 4 unit.
The different parameters of effects vary with both of the machines. While the Vocalist 2 offers only a limited selection of vocal enhancement effects, the Vocalist 4 excels with five additional vocal enhancement parameters such as Preamp, Compressor/Gate, EQ, Lead Effects and Harmony.
The Guitar Reverb and Chorus parameters on the Vocalist 4 outshine the basic processor effects of the Vocalist 2. The separate harmony and pedal effects on the Vocalist 2 aid in transforming multiple signals; however, the four adjustable parameters of Pitch Correction on the Vocalist 4 offer more versatility.