Which pedal should I get: Boss DD-7 or MXR Carbon Copy Deluxe?

The Boss DD-7 as well as the MXR Carbon Copy Deluxe are two popular delays. Both have some similarities (tap tempo, modulation) but actually, they are fundamentally different.

Boss DD-7

The DD-7, one of the most successful pedals and part of the legendary DD-series, is a digital delay.
Besides very good digital delay sounds, it also offers an analog delay mode. It is digital emulated and is sonically oriented to the darker sounding analog delays.
The pedal is pretty robust, compact and easy to handle. Not for nothing, this Boss delay is a standard on many pedalboards.

MXR Carbon Copy Deluxe

The MXR Carbon Copy Deluxe is a pure analog delay. It has a dark- and a bright- mode. But the bright-mode is not as brilliant as a clear digital delay. The pots for speed and depth allow to control the modulation quite sophisticated and thereby offers numerous effect-variations. It is even possible to create a chorus or vibrato effect.
Especially for oscillation, this analog delay is pretty famous.

It depends on your needs

Although the Boss DD-7 also offers a modulation delay, it is not possible to adjust the intensity and especially with long delay times, to me, it is too intensive.

If you want to choose between both pedals, it depends on the individual style of playing and the kind of music you want to create.
For those who are looking for a dark delay that drifts in the background and leaves enough room for the guitar and you prefer a discreet modulation that makes the guitar sound even more three-dimensional, an analog delay would be perfect. Also, if you want to thicken the lead tone.

For more percussive delays that interact rhythmically with the pedal, I would recommend the digital delay. It creates clear repeats that are famous for many styles of music. But the analog mode of the DD-7as well is considerably good. The delay sounds organic and is more than a darker digital delay.
Thus, the DD-7 is the perfect allrounder which is able to create percussive and striking delay pattern for one song and by using the analog mode, offers discreet background-soundscapes for another song.

And if you can’t decide

For those, who have enough space on the pedalboard, a combination of both pedals can be very interesting as well: The Boss DD-7 for digital sounds and the MXR Carbon Copy Deluxe for the analog sounds.
An exciting fact is, that the tap jack of the MXR Carbon Copy Deluxe is able to send a tap signal to another pedal and also to receive the signal. This function can easily be activated.
Thereby, only one pedal has to be tapped to make both pedals work at the same tempo. And by, the additional activation of one of the numerous subdivisions of the MXR Carbon Copy Deluxe, you can activate both delays at the same time and thereby combine dotted eighths (CCDLX) with quarters (DD-7).
In the signal chain, I would place the DD-7 behind the Carbon Copy Deluxe, for the digital delay does not affect the signal, while the analog delay would cut the treble of the digital delay sound.
Furthermore, you will get the option to use the stereo outputs of the DD-7 at the end of the signal chain to send the signal to two amplifiers.