ATI or NVIDIA

I want a gaming laptop.My budget is around 80k. Im'm thinking to buy a dell studio xps 16 as its gotta a very nice config.1000 fsb t9550 and 3gb ddr3 ram backlit keyboard and gud screen res. 1366*768 but the prob is they are giving ATI Mobility RADEON® HD 3670 - 512MB for graphics......i dunno much about the ATI and NIVIDIA fight but usually i found nividia cards and i usually played on them.But still if i got a DELL XPS M1530 which has NVIDIA® GeForce® 8400M GS or 256MB NVIDIA® GeForce® 8600M GT then which is gud?

I did some searching also.i found a site which has got nice info about the notebook graphic cards and all....here are the links...
http://www.notebookcheck.net/NVidia-...GS.3709.0.html and http://www.notebookcheck.net/ATI-Mob...70.9595.0.html

And i heard rumours also that if you bought the ati card crysis and all the games which shows nividia logo at their starting or on game pack wont run well...they lags.....same is with ati......if you run other game which supports ati....then it wont work gud with nvidia cards.....can you please tell me is this a rumour or truth...?

And also if you people have any other gaming laptops in your mind considering the budget please tell me...

and ya i forgot to post this....
http://www.notebookcheck.net/NVIDIA-...GT.3986.0.html

MSI GT725-074US 17-Inch Laptop (2.4 GHz Intel Penryn Core 2 Duo P8600 Processor, 4 GB RAM, 320 GB Hard Drive, ATI R4850M Graphics, Vista Home) is the best gaming laptop for you. also you can see here for more details http://forums.techarena.in/portable-devices/1086288.htm

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I'll buy laptop from delhi mostly.....msi and asus gaming laptop is also gud.but how i should compare the graphic cards.i mean i know 8700 is better then 8600 but when comes the 9xxx series i starts confusing.i checked the reviews in notebookcheck.net.in that site these guys compare graphic cards through 3d benchmark05
for 8600m gt i got 6175
for ati radeon mobility hd3670 7284
for nvidia 8400m gs 2671
and i think all of this dell xps studio i found the best as the hardware is the coolest one its coming in 77k but the problem is graphic card only....
and yeah you people didnt tell me about this nvidia or ati rumour...?