which configuration is cheaper?

i am looking to buy a lenovo z510. i have found a 4gb version for £500 and a 8gb version for £600. i really want a 8gb ram so do you thinks it cheaper buying the 4gb version and upgrade the ram manually or shall i just buy the 8gb version. and also, if i pick the 4gb version which ram is recommended to buy to upgrade to 8gb.thanks

may be needed:
4gb version: Lenovo Z510 15.6-inch Laptop - Black (Intel Core i5-4200M 2.5GHz, 4GB RAM, 1TB HDD, Nvidia GT 740 1GB, DVD RW, Windows 8.1): Amazon.co.uk: Computers & Accessories

8gb version: Lenovo Z510 Intel® Core™ i5 Processor, 8Gb RAM, 1Tb Hard Drive, 15.6 inch Laptop with 1Gb Dedicated Graphics - Black | very.co.uk

 

If the only difference between the two is the memory, then I do believe 8GB of RAM should cost less than £100...

If it's close (which it might since you're not in the US), you can always sell the old 4GB to make up some of the difference.

 

For money worth it will depend what O/S is installed if it is x86 forget getting higher then 4gig if x64 4-8gig would be good to have but if your apps don't need alot then go with 4gig unless final price difference isn't too big. But I gotten along fine with Windows 7x64 Ult Sp1 with 4gigs.

 

I have no idea about Lenovo so its best to check first if the supplier lets you upgrade the ram yourself without voiding warranty as quite a lot of company's have void stickers on most of the hardware.

 

i would always go for the highest amount of ram possible, programs nowadays gets heavier and heavier with every update, since the most horrible thing to experience on pc is to use too much virtual memory ( = mega-lagging)
even worst if you get Win7.

however, if you want to add yourself ram, it'd be wiser to know more about the components (number of slots, ram brand/type/size) on the manufacturers website.

 

That makes much sense as not making any sense. Your grabbing for straws that has no evidence behind it or to even inform us where your getting that stats from. More memory doesn't equal more work when your O/S can't access RAM above 4gig that is a waste of money and RAM. Sounds like you need to redo your settings if your VM is taking too much RAM. I never seen my VM affecting my system performance and if your taking a hit from VM then something else is wrong with your system setup.

This is why we need hardware Product Number or Exact Model number otherwise no one knows what users are asking about. That is why I said we looking for a needle in haystack.