Would you be buying the cob version? If so I used to have Thorowgoods, T4 for my youngster and T6 for my cob. Fab saddles, so much so I've bought the Kent and Masters leather versions of them for all three of my horses, cob, gp and high either purely because they are so adjustable and I just love them
Saddle Company saddles look nice and they are adjustable but you can't alter the fitting yourself. You need to get an SC fitter with a special tool to do it and they can charge from £60 per visit. Also, some fitters are better than others!
On balance I think I would go witjh the synthetic.
I have recently had a T4 fitted to my growing 4 yr old, I asked the saddler what he tought of the saddle company saddles, he said he didn't like the way they adjust them, as the metal bar in the front of the saddle is stretched and pushed to adjust it, and metal when it is subjected to this can crack.
I've got both, love both! out of preference would opt for the saddle company as they are more adjustable and part or full leather depending on the model, but am very pleased with the fit of the t4 pony club saddle i've just got for my boys pony too.