Benefits of newer racer bikes over older ones?
TL; DR: There is going to be a lot of difference. A 1500 Euro bike today would probably be comparable to a 6-7000 Euro bike from 10 years ago.

Elaboration:

There are going to be quite a few improvements in the bike due to technology advances and research and development. Some of the base models will not be radically different from your frame, although even there, there are some differences. 

First is frame composition, in that quite a few (even entry level) racing bikes are now all carbon. This is enabled as when a bike is first created, there are a lot of research and development costs that have to be offset. After a few years, that is offset, and the "top" model often becomes the "middle" model as a new frame is developed for the high end of the scale. 

Here are a couple of rides that are fairly similar in shape, and are entry level road bikes. Note the Giant has the cutout (1500 Euro), and the Specialized Allez does not (1250 Euro). The Allez is aluminum, the Giant is carbon.




Second is the frame shape and tube shapes. For the entry level, you may not see a lot of difference (Especially in the known name brands), but almost all still have top tubes that slope downward towards the seat tube, and a few have smaller cutouts for the rear wheel. When you move up the price ladder, tubes start changing shape, and aerodynamic considerations become much more dramatic. 

As you can see in the Specialized Venge below, the top tube slopes away from the headset, and the seat tube is notched much more than the entry level rides to accommodate a tire being closer and more protected, which increases aerodynamics. The tubes are also more oval/wing shaped, rather than round.



If you want to step up in price, you can look at the Cervelo S5 (Cervelo is arguably the best bike company around for understanding aerodynamics), which has a much more protected rear wheel, the forks more integrated with the frame, and much cleaner lines throughout.


The final area is the trickle down technology in the groupsets, which consists of your derailleurs, brifters (brake/shifter combination), brakesets. The Shimano 105 and SRAM Force groupsets, which you typically find on the more entry level bikes are comparable to the Dura Ace and Red groups of 4-5 years ago, and as the top levels advance, the technology of the former top groups starts falling down to the next tiers below.

In bikes, you can have light, cheap and reliable. You get to pick any two from that list.