Side by Sides ( SXS's) are not seen much on any clay target field.
Your sight picture changes when you're shooting a SXS - as opposed to a stacked barrel like an O/U. O/U's are by far the dominant gun on Skeet, Trap and Sporting Clays fields ....and have been for many years.
The trend today / on competition Skeet or even casual Skeet guns is O/U's with 30" barrels - and often with a gross weight of around 8 - 8 1/2 lbs. 28" barrels are ok today too / but the trend yrs ago was for 26" barrels and you won't see anyone under 60 yrs old / shooting 24" or 26" barrels anymore either.
You should take some guidance from your uncle / especially since he wants to take you around to some gun shops / and spend some time at your local club too - talk to some of the better shooters - see what they're shooting / would they buy the same gun again / get some pros and cons.
Personally, my primary gun for Skeet, Sporting Clays and bird hunting - is a Browning Citori, XS Skeet model, with an adj comb built in. It has a lot of adjustment / and that model of Browning Citori will fit 99% of the shooters out there. Its a lot of gun for the money / not a real high end competition gun / but a very serviceable gun that will last 2 or 3 generations and easily for 100,000 shells or more before any rebuild is necessary.
http://www.browning.com/products/ca...tent=citori-xs-skeet-adjustable-comb-firearms
I have that same gun in 12ga, 20ga, 28ga and .410 / all in 30" barrels ( with my 28ga and .410's built on the 20ga receiver ). Not the best way to go for a serious competitor that wants to shoot exactly the same gun, same balance, etc in all 4 gagues / but it suits me - and I like to have the stand alone guns.
http://thefiringline.com/forums/attachment.php?attachmentid=62169&d=1281543688
New, this model sells for around $ 2,750 - $ 3,000 and there are a few of them around used from $ 2,000 - $ 2,500 / but its a gun that will last a long time / and if you take care of it - will have a lot of re-sale value down the road. Its a very versatile gun..