The 2nd generation has better performance** and several new features. For example, if you are just comparing the i5-2540M with the i5-540M, you will see that the new 2nd gen graphics has been integrated on the same die as the processor core and therefore has higher graphics frequency for betterperformance. The 2nd gen Max Turbo Frequency is also higher for better performance. The 2nd generation processor also supports faster memory bandwith and faster DDR3 memory, tubo 2.0, and other features like the AVX instructions. With the 2nd gen processor you also can get Intel Anti-Theft 3.0 and Intel AMT 7.0 in the Intel vPro Technology models.
The 2nd generation has a new "badge" that you might see on the outside of the laptop (it's up to the OEM to put it on) but it has a zig-zag stripe on it. You can see the new badges for i3, i5, i7, and i7 extreme edition here: http://www.intel.com/consumer/products/processors/core-family.htm
To compare the detailed processor specs go to http://ark.intel.com and use the checkboxes to select the processors then click on the compare button at the top.
For example, to compare the i5-2540M and the i5-540M mobile processors see the following: http://ark.intel.com/Compare.aspx?ids=43544,50072,
**Your performance depends on many factors so please check out our results for industry standard benchmarks and the details on the performance claims, see: http://www.intel.com/performance This site has specific results for 2nd generation Intel Core processors.
Yes, apart from looking for the '2' at the beginning of the model number. As far as I am aware these are the different logo's to tell 1st and 2nd generation apart.
1st gen logo:
Notice the the right top curved area exposing the inside chip.
2nd gen logo:
Notice cut through the mddle showing the chip inside.
Hope this helps,
(correct me if I'm wrong anyone, but this is how I've been telling them apart)