Need some insight: trying to Decide on a portofino automatic watch

All I am close to becoming a IWC owner. I saw a Portofino automatic IW356504, which I think is a classy watch. Now I must admit it is several thousand dollars more than I am willing to spend. In doing my research I came across an older model: IW356302. The older model is 39mm vs 40mm, which is fine for me. Also the depth on the older model is slightly smaller, which is also good for me. Other differences: The newer model has: 35110 Calibre and 25 Jewels. The older model has 30110 Calibre and 21 Jewels. In this area I am out my depth. Can someone let me know if there is a major difference between the calibres and the # of jewels? The other question is that the older model seems (at least in the US) to only come with a black wristband where the newer one has brown. I won't buy the watch without the brown strap. I'm assuming this is easily rectified by buying a brown IWC strap and having it installed. I find it surprising that the older model with the brown strap is available in Europe but not the US.

Also, The newer model has a beautiful engraving on the back of the case, but once again I don't know if it justifies the huge price difference between the old and the new.

I'd appreciate insight on these questions as well as any other insight on this beautiful watch.

Thanks

Rindge - These are both very classy watches and even though I am not an expert on the different movements I would not place much importance to the different numbers of jewels etc. These are both high quality IWC watches.
I would choose the one that speaks to you and which you find agreeable with what you have or are willing to spend. I am 99% sure you can get a brown IWC strap for the 356302, but check with your Authorized Dealer (AD) to be sure. I believe the lug width on those two Portofinos are identical - but as an amateur I am not dead certain.

Good luck!!