...SEGA would disagree, gamegear anyone?

its still a little early to tell

This topic deserves a lot more credit than people here have given it.

There were many theories before the release of both consoles, that they are mimicking the patterns of their handheld cousins - and there hasn't been much to discredit these theories yet:

PSP / PS3

 - more expensive, premium solutions

 - aimed more at hardcore gamers, young male demographic 

 - "hit" driven software sales (big hits sell well, other titles not so well)

 - pushing their own non-standard disc format

 - favour graphics over input innovation

 - software sales struggling (relative to other machines)

DS / Wii

 - cheaper solution

 - more casual, family orientated titles

 - better "across the board" sales (cheaper, simpler titles tend to sell ok - MySims, Carnival, etc)

 - not aimed at pushing new "tech standards" on to consumers

 - weaker graphics, innovation in input ("fun")

 - strong software sales

...

The main advantage the PS3 has over the PSP (and its a big one) is this: the PSP aims at being a portable console, around PS1/PS2 tech power. Not that many "original" games are created for the platform, and many of the ones that are - are eventually ported to the PS2 (etc...).

The PS3 is the "top" of the gaming chain - it will have more original, exclusive titles - and games that haven't been seen before, and can't be easily ported down.

The main disadvantage the PS3 has over the PSP - extra competition. Whereas there are only two handhelds - the PS3 is also competing against the 360, PC & PS2 devices.

...

In conclusion - I wouldn't be at all surprised to see the same "patterns" continue in the future. The PSP hardware is selling well - and the PS3 hardware will also sell well.

However, the DS is killing the PSP in hardware sales terms - and I expect the Wii to do the same to the PS3 (which it already is) at least in the foreseeable future.

... 

More important will be software performance. To date, the PS3 has significantly underperformed in terms of software sales - the Wii has done pretty well, and actually created some hit new franchises (with sales hits - WiiSports, MarioParty8, WiiFit being some obvious ones that come to mind).

To date in Japan: The Wii has sold 11m software units, and the PS3 around 3m - no pack-ins, and both released around the same time.

Worldwide - this site has 11 1m+ sellers for the Wii, and just 2 for the PS3 - both of which were launch titles, and heavily included as "pack-ins" in various bundles over the last year.

The PSP has 11 1m+ sellers - and the DS has 35. Similar ratios to their console brothers.

Wonderswan, Gamegear, pocketstation even the N-Gage have done more than a million

@Shams, see thats what this post needed in the first place. Some logical discussion about why they are similar not just going 'Hey the Wii is like the DS and the PS3 like the PSP....' 

what are they superior at besides tech

even the atari lynx sold more than a million.  As if Leo-j couldn't look any more dumb than he already does.