I am going to do a 3-Way comparison between the Kenwood KDC-MP342U and Pioneer DEH-3100UB and Pioneer Premier DEH-P310UB.

First off Price.

The KDC-MP342U sells for around $140.

The DEH-P3100UB sells for around $150

The DEH-P310UB sells for around $170

Here is the Specs for the DEH-3100UB

General features:

• CD receiver with built-in MOSFET amplifier (14 watts RMS CEA-2006/50 peak x 4 channels)
• plays CDs, CD-Rs, and CD-RWs, including discs loaded with MP3, WMA, and AAC files (except rights-protected files)
• remote controlAudio features:
• Advanced Sound Retriever (ASR) for improved sound quality from compressed music files
• Easy EQ 3-band parametric equalizer with six preset tone settings
• loudness
• low-pass (preamp outs) and high-pass (speaker and preamp outs) filters
• subwoofer level controlExpandability:
• built in iPod control — no adapter necessary, but adding Pioneer's optional connecting cable lets you leave your iPod cable at home
• compatible with optional Pioneer Bluetooth adapter, HD Radio tuner, satellite radio, CD changer
• inputs: front panel auxiliary and USB inputs
• outputs: 4-channel (2 Volt) preamp outputs (front, rear/subwoofer)Other info:
• compatible with most factory steering wheel audio controls (adapter required)
• CEA-2006 compliant amplifier
• warranty: 1 year

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Here are the specs for DEH-P310UB

General features:

• CD receiver with built-in MOSFET amplifier (14 watts RMS CEA-2006/50 peak x 4 channels)
• plays CDs, CD-Rs, and CD-RWs, including discs loaded with MP3, WMA, and AAC files (except rights-protected files)
• remote controlAudio features:
• Advanced Sound Retriever (ASR) for improved sound quality from compressed music files
• Easy EQ 3-band parametric equalizer with six preset tone settings
• loudness
• low-pass (preamp outs) and high-pass (speaker and preamp outs) filters
• subwoofer level controlExpandability:
• built in iPod control — no adapter necessary, but adding Pioneer's optional    connecting cable lets you leave your iPod cable at home
• compatible with optional Pioneer Bluetooth adapter, HD Radio tuner, satellite radio, CD changer
• inputs: front panel auxiliary and USB inputs
• outputs: 4-channel (4 Volt) preamp outputs (front, rear/subwoofer)Other info:
• compatible with most factory steering wheel audio controls ( adapter required)
• CEA-2006 compliant amplifier
• warranty: 2 years

Here is the specs for KDC-MP342U

General features:

• CD player with built-in MOSFET amplifier (22 watts RMS/50 peak x 4 channels)
• plays CDs, CD-Rs, and CD-RW discs, including discs loaded with MP3 and WMA music files
• detachable face with illuminated USB input
• iPod direct control via USB input — no adapter necessary, but adding Kenwood's optional KCA-ip101 cable lets you leave your iPod cable at home
• remote controlAudio features:
• System Q Sound Control (6 EQ curves and a 3-band equalizer)
• low-pass filter and sub level controlExpandability:
• compatible with Kenwood's Bluetooth adapter, HD Radio tuner, satellite radio
• inputs: front-panel USB and auxiliary inputs
• outputs: 4-channel preamp outputs (front, rear/sub)Other features and specs:
• warranty: 1 year
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The KDC-MP342U retains the new slick look from KDC-MP242. The new features this radio adds is a front USB and Aux Input on the right hand side. The channel and track forward buttons to the right of the Volume knob. Along with the FM/AM buttons. The display shows only track, or frequenty or time, but not both. Although if the clock button is pressed it will show up after a few seconds, leaving just the clock on the display.

The DEH-3100UB and the DEH-P310UB both have the sleek polished look. Giving it a shine. The buttons around the earlier models have been replaced with a 7-way Rotary Commander. Which mean you can use it for volume, changin channels, select am/fm, track forward, scroll through you music easier, as well as menu selections. While I think ingenious, a good pot hole in the road, could help you select something you was not looking for. Gone are the days where there was a button for everything.

The DEH-3100UB/DEH-P310UB add iPod Control, through use of a in front of the radio USB cable and includes an iPod cable in the box with the radio. The KDC-MP342U, does not have an included iPod cable, but also includes a USB on the front, which I think it pretty dog gone handy.

The DEH-3100UB/310UB now includes readiness for HD radio, and Satellite radio, both sirius and xm. Although you have to purchase modules for that.

All three radios have a front AUX input. Great for anything other than an iPod, that provides sounds through headphone jacks.

The DEH-3100UB has a 1 Year warranty and a 2 (2.2volt)front/rear w/ switchable subwoofer output preout. The DEH-P310UB, which is a Premier, has a 2 Year warranty and 2 (4 Volt) front/rear w/ switchable subwoofer output Preouts. The KDC-MP342U has 2 (2volt) front/rear preouts w/ switchable subwoofer output, and a 1 year warranty.

On all three radios, the path to change to bass, mids and treble, is the same. All you have to do is push in the volume knob, and you can cycle through bass, mids, treble, balance, and fader. To make a change all you have to do is turn the knob.Because of the 7-Way rotary commander, it will take some extra skill, to make sure you are giving the right command.

Both the Kenwood KDC-MP342U and Pioneer DEH-3100UB/DEH-P310UB both have a AME (Kenwood) and BSM (Pioneer) to automatically set the next six strong FM stations to your presets.

For cosmetic appearance:

The KDC-MP342Uhas improved the look with a much more organized face with nice bright blue illumination and white lettering on display. The DEH-3100UB/310UB have a sleek, more on the chromish side face, with green illumination and a white lettered display.

Overall Recommendations:

KDC-MP342U

Ease of Use: 8

Appearance: 7

Performance and Features: 7

Pros:

Easy menu setup and the ability to change eq settings. The Front USB makes it easy to hook up a iPod or 8 gig thumbdrive

Cons:

This radio does not come with a 2 year warranty

DEH-3100UB/310UB

Ease of Use: 6

Appearance: 7

Performance and Features: 7

Pros:

Very nice face, sleek appearance. Having a USB on the front is a plus. Has an included iPod cable for iPhone and iPod users. Improved accessibility to the Bass/Mid/Treble controls. 2 Year warranties are awesome.

Cons:

Less buttons on the face, it is harder to set favorite fm/am channels.

My Thoughts:

While the KDC-MP342U adds a USB on the front, and more ease of use for features, I believe the Pioneer DEH-3100UB and the DEH-P310UB would get my vote for the included iPod Cable. Also out of the 3 I would have to choose the DEH-P310UB for it's two year warranty, and higher volt preouts.