[Dell Streak 7] Z4nd4r:
I own both the Galaxy Tab and the Streak 7, so I can comment on this with a little authority (as can docfreed). Let's take the issues one at a time:

Screen-

Admittedly, the Streak 7's screen isn't the best. The Galaxy Tab's is pretty awesome (at least as good as the iPad's, in my experience). That said, the Streak 7's screen is actually not that bad. I find that, aside from one issue, there is no difference in real world usage between the S7's screen and the Tab's. Unless you have them side by side, you wouldn't know the difference (other than the one issue I'll get to). In fact, I actually prefer the contrast ratio of the S7's screen to that of the Tab.

The one issue the Streak 7's screen has is viewing angles; well, one viewing angle. If you have the S7 held in landscape mode, the angle that would be "down" is pretty poor. This can affect "left" in portrait mode, too. I find the only time it's annoying is if the S7 is flat on a desk in front of you, but this can easily be managed by either flipping it upside down (where there is a nice viewing angle; the screen will auto rotate) or by using the media dock (if you get a Streak 7, get the media dock; it's really nice).

Performance-

Between the Streak 7 and the Galaxy Tab, there's absolutely no comparison. Streak 7 creams the Tab in everything imaginable. I don't care what the Quadrant scores are (that benchmark is really dated and not very useful); the Streak 7 positively blows the Galaxy Tab away.

Battery Life-

No contest. The Galaxy Tab wins, hands down. The Streak 7's battery is less than 3/4 the size of the Tab's, plus I think there's a problem with the performance optimisation (I'll be posting a thread on it here, soon). I personally use the S7 for my main device; that's for all computing (other than work), internet browsing, phone calls, media consumption, gaming, photos; you name it. I don't find the battery life to be an issue, but I do end up charging a lot. My wife can go all day and into the next with her Galaxy Tab on a single charge.

Internet Connexion-

This one's a toss up, in my area. T-Mobile 4G is way faster than Verizon 3G, with about the same coverage, but Verizon's connexion is more reliable. Your mileage may vary depending on where you live.

Interface-

The Streak 7 runs vanilla Android FroYo with a custom launcher (Dell Stage UI). Add any launcher (LauncherPro, ADW Launcher, Zeam, etc.), and you're on stock Android. The back end is all stock. I personally run Zeam in a 6x6 grid and find it perfect.

However, this will not appeal to all. There's a reason I got my wife a Galaxy Tab and not a Streak 7, and battery life/screen wasn't all of it. TouchWiz, as much as we Android faithful hate on it, is actually pretty nice for the average consumer. The little touches like the coloured menus and the text pointer (which Android fixes in Gingerbread/Honeycomb, but are still bo-bo on FroYo) are a real boon to many users. If you want an easy experience over upgrades and raw speed, TouchWiz is actually pretty nice.

So, which would I recommend? If you're on XDA, the Streak 7 is probably your winer. It's faster in every way, and will stay relevant in the coming months. If you'd rather all day use and a seamless experience (or if you're really into ROMs and themes, which are in short supply on the S7 but plentiful n the Tab), go with the Galaxy Tab.

Only you will know which choice is right for your needs, but I hope I helped shed some light a little on what those choices really entail.