[Galaxy Tab 10.1 General] flarbear:
I have both here and wanted to compile a list of differences for those who are curious. I don't have time now to take some pictures, but I'll describe the main differences I've noticed and hopefully update this over the weekend a couple of times if there is any demand.

Results unique to the Wifi version are highlighted in blue.

Results unique to the 4G/LTE version are highlighted in red.

Hardware:

Both have:

Texture and colors are identical (both are 32GB dark gray versions)

identical dimensions to the accuracy of my finger tips measuring

headphone jack slightly right of center on top bezel

data/charging connector centered on bottom bezel

3MP camera at top center of back

2MP camera slightly to the right of top center on front

microphone hole about an inch to the right of the data/charging connector

Wifi model has:

Power on left side of top bezel

Volume rocker to right of power on top bezel

speaker openings about 80% up each side bezel

two things that look like screw hole covers on each side of the data/charging slot

SVMSUNG styled logo just above center on back

CE and fine print bottom center of back

4G/LTE model has:

Power on left bezel approximately where Wifi has left speaker

Volume rocker just below power on left bezel

speaker openings about 75% as long as the Wifi model's and about 1/2 inch higher on each side bezel

micro-sim door about 1/2 inch to right of headphone jack on top bezel

(checkmark)verizon styled logo where Wifi has SVMSUNG logo

4G/LTE logo and fine print bottom center where Wifi has CE text

SVMSUNG styled logo just above 4G/LTE (aka CE fine print) area

System:

Wifi "About":

Model number: GT-P7510

Android version: 3.1

Kernel version: 2.6.36.3, se.infra@sep-58 #1

Build number: HMJ37.UEKF3 P7510UEKF3

4G/LTE "About":

Model number: SCH-I905

Android version: 3.1

Kernel version: 2.6.36.3, se.infra@SEI-20 #1

Build number: HMJ37.EG01.SCH-I905.EG01

UI:

Wifi offers "Silent Mode, Flight Mode, and Power Off" when you long press the Power button. The 4G/LTE version offers "Silent Mode, Airplane Mode, Restart, and Power Off".

ZoinksS2k mentions: The LTE's power button is almost impossible to find by touch alone. You have to drag your finger past the speaker slot and hope you find it. It is fairly annoying.

4G/LTE web browser has a Mobile/Desktop view mode setting.

4G/LTE web browser has the Labs tab in the browser settings.

Software:

Wifi has a Samsung update procedure, 4G/LTE appears to have an Android update experience there (but I'm not sure I'd know what was stock). Both are accessed via Settings->About->System Updates.

4G/LTE version offers Automatic date/time option in System settings.

Both have the same looking Samsung camera app

4G/LTE came with Google Videos with access to Google Movie store, Wifi does not have access to the app

Wifi came with Samsung Apps store, 4G/LTE does not have it

Both were ready to download my paid apps when I went to the Market after activating them, but neither downloaded all my other apps (the Xoom I was using downloaded every app I had on my phone when I first logged in with it).

Performance:

In the parking lot outside the Verizon store I saw 23694dn/7052up/51ms ping on one try and 22027dn/8246up/49ms ping on a second try. At home I got around 12000dn/6000up/<50ms ping reliably. My home Wifi usually measures 15Mb/5Mb/18ms on both tabs for comparison, though I did get one reading of 20Mb down (on Comcast Blast! which measures 36Mbit down and around 5-6Mb up using my desktop computer).

Benchmarks (some results revised after restarting the tabs with no home-screen widgets):

Startup times (from pressing power to first graphic, first animation, lock screen):

Wifi gets (6.4s, 13.8s, 34.9s), (6.6s, 14.2s, 35.6s), 4G/LTE gets (6.1s, 16.8s, 47.3s), (~6s, 17s, 44.5s)

(Note that around the 33s mark both tabs would blip the haptic feedback sensor - the Wifi version would then show the lock screen within a second or so after that, but the 4G/LTE version would take another 10 seconds or so with the animation being slightly slower and a bit laggy before it would get to the lock screen - this could be the time when it is registering on the 4G network even though it happened whether wifi or mobile data was on or not, but Airplane mode did cut off about 3s from the total time to the lock screen.)

Nenamark1: Wifi gets 31.3fps consistently, 4G/LTE gets ~42fps

Nenamark2: Wifi gets 19.1fps consistently, 4G/LTE gets 19.3fps consistently

Linpack Single Threaded: Wifi gets ~31, 4G/LTE gets ~30

Linpack Multi-threaded: Wifi gets ~30~57, 4G/LTE gets ~56

Vellamo: Wifi gets 952, 967, 4G/LTE gets 957, 955

Quadrant advanced results (3 runs each):

aaaTotal:aaaa1405, 1588, 1686aaaa2232, 2440, 2490 averages 53% faster

aaaCPU:aaaa3295, 4081, 4531aaaa3403, 4158, 4371 averages within 1%

aaaMemory:a1928, 1847, 1954aaaa1895, 1879, 1839 averages 2% slower

aaaI/O:aaaaaai923, 1128, 1060aaaa4788, 5106, 5174 averages 384% faster

aaa2D:aaaaai0260, 0265, 0267aaaa0261, 0259, 0258 averages 1% slower

aaa3D:aaaaai0618, 0620, 0618aaaa0811, 0799, 0807 averages 30% faster

AnTuTu results (3 runs each):

aaaRAM:aaaaaaaaaa0821, 0815, 0821aaaaa0817, 0812, 0819 averages within 1%

aaaCPU Integer:aaaa1173, 1165, 1173aaaaa1168, 1161, 1170 averages within 1%

aaaCPU Float:aaaaai1016, 1008, 1018aaaaa1013, 1014, 1016 almost dead even

aaa2D Graphics:aaai0292, 0291, 0293aaaaa0293, 0293, 0293 averages within 1%

aaa3D Graphics:aaai0795, 0797, 0795aaaaa0853, 0859, 0847 averages 7% faster

aaaDatabase I/O:aaa0265, 0370, 0330aaaaa0390, 0460, 0450 averages 35% faster

aaaSD card write:aa009.1,012.0, i11.9aaaai007.5,007.6, 0i7.3 averages 47% slower

aaaSD card read:aa020.3, 021.8, 18.5aaaa012.8, 010.5, i13.0 averages 67% slower

aaaTotal score:aaaai4642, 4756, 4733aaaaai4737, 4780, 4798 averages 1% faster