I am going to do a comparison between the Kenwood KDC-MP442U and Pioneer DEH-4100UB.

First off Price.

The KDC-MP442U sells for around $160.

The DEH-P4100UB sells for around $170

Here is the Specs for the DEH-4100UB

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)
• detachable face with 16-character Organic Electroluminescent (OEL) display
• remote controlAudio features:
• Easy EQ 3-band parametric equalizer with six preset tone settings
• Advanced Sound Retriever improves sound quality of your digital music files
• loudness
• high- and low-pass filtersExpandability:
• built in iPod control — no adapter necessary, but adding Pioneer's optional (CD-IU50 cable) lets you leave your iPod cable at home
• compatible with optional Pioneer Bluetooth adapter, HD Radio tuner, satellite radio, CD changer
• inputs: front auxiliary input, rear USB input (for Windows Media devices, USB storage devices, and iPod)
• outputs: 6-channel 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 KDC-MP442U

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 files
• detachable face with with 13-character display
• remote controlAudio features:
• dual-zone capability for playing different sources over the front & rear speakers
• System Q Sound Control (6 EQ curves and a 3-band equalizer)
• Supreme Setting function restores high frequencies in music files
• System E's high- and low-pass filtersExpandability:
• 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
• compatible with Kenwood's Bluetooth adapter, satellite radio, and HD Radio™ tuner
• inputs: front auxiliary and USB inputs
• outputs: three sets of 2.5-volt preamp outputsOther features and specs:
• compatible with most factory steering wheel audio controls (adapter required)
• warranty: 1 year
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Looks:

The KDC-MP442U has changed its appearance from the previous KDC-MP342U. It also adds a covered compartment on the right hand side, opaquely concealing illuminated Aux and USB Inputs. There is a door that slides down out of the way, exposing the inputs. Two shiny silver bands wrap around the volume and the Aux/USB input compartment enhancing the radio's looks. The preset channel buttons have been taken away, and a Search, Favorites, and Src buttons were in their place.

The DEH-4100UB has the sleek polished look, but also adding shinier areas, than the previous DEH-P3100UB/310UB radios. The extra chromish areas, give this radio a higher, more expensive look. The DEH-P4100UB retains the use of the 7-way Rotary Commander, for joystick/menu control. Just push in, turn the knob, and select different features. 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. For those of us who work with menus, and computer software all day, will get used to new 7-Way Rotary Commander.

Features:

The DEH-4100UB adds iPod Control, through use of a behind the radio USB. This time the radio does not come with a iPod cable in the box. The KDC-MP442U, also does not have an  iPod cable, but includes a USB on the front, which I think it pretty dog gone handy. Although the rear cable does give you the flexibiliy when you add the optional CD-IU50 cable, to route it to a location more secluded, i.e.; glove box, center console, giving the radio its good looks without having a cable poked in the front.

Both the KDC-MP442U and DEH-P4100UB have support for HD radio, and Satellite radio, both sirius and xm. Although you have to purchase modules for that. They also include support for MP3, WMA, and AAC, Apples version of compressed format. The DEH-P4100UB employs the use of ASR, Advanced Sound Retreival, when this is turned on, the music coming from compressed files, is enchanced, to near CD quality.

The Kenwood KDC-MP442U includes a Supreme Setting, which can be turned off/on, also provides higher quality music playback. This radio also features a Music Search feature which allows you to scroll through and select your MP3/WMA music folders and files, as well as scroll through your audio CD's music tracks using the headunit's rotary knob. This radio also provides a new feature called Favorites. You can set your favorite iPod playlist, fm/am station, satellite channel, or even phone numbers when you use the optional Bluetooth module.

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

The DEH-4100UB has a 1 Year warranty and 3 (4 volt) front/rear/subwoofer preouts.

The KDC-MP442U has a 1 Year warranty and 3 (2.5volt) front/rear/subwoofer preouts.

For cosmetic appearance:

The KDC-MP442U has less buttons on the face with nice bright blue illumination and white lettering on display. The DEH-4100UB have a sleek, even more chrome, than the previous models, with blue illumination and a blue lettered display.

Overall Recommendations:

KDC-MP442U

Ease of Use: 7

Appearance: 7

Performance and Features: 7

Pros:

Easy menu setup and the ability to change eq settings. Big buttons on the face, make it easier, to scroll through your music. The Front USB and Front Aux makes it easy to hook up a iPod, 8 gig thumbdrive, or other audio source.

Cons:

The loss of preset channel buttons make it alittle harder to set stations.

DEH-4100UB

Ease of Use: 7

Appearance: 7

Performance and Features: 7

Pros:

Very nice face, shinier, sleek appearance. Having a USB in the rear, makes it a neater installation, by routing the cord to another location. Improved accessibility to the Bass/Mid/Treble controls.

Cons:

The absense of the ipod cable, will make it harder for someone to hook theirs up without using their own white iPod cable or having to purchase another one.

My Thoughts:

These two radios are almost head to head in features, looks, and ease of use. Both radios feature a multiuse joystick style volume knob, that can use be used for most features. The absense of the iPod cable for the box, has turned my pick of radio to the KDC-MP442U. Because this radio can use the white cable you have at home, merely by plugging it is. With the USB in the rear of the DEH-P4100UB, it is harder, if you do not buy an extra cable, to plug you iPod in.