Comparing your size to sizes of panels on ebay yours looks to be in the ball park for 200w. I expect that panel sizes for a nominal wattage will vary a little, depending upon manufacturer , panel type & panel efficiency.

200w 1460mm x 940mm = 1373400 sq mm
http://www.ebay.com.au/itm/200W-SOLA...item5669fe4a3e

200w Your panel
1200 x 1000 = 1200000 sq mm

200w 1320 x 990 = 1306800 sq mm
http://www.ebay.com.au/itm/200W-Mono...item4187aa1665

It is possible your panel is either more efficient or a bit less than 200w

Also possible that your mates 250w is not 250w.

There have been panels sold on ebay & elsewhere that are lower wattage than advertised.

Only real way to check is to set up both panels, connected to a discharged battery & measure the amps being fed into the battery. Needs to be done at the same time so sun condition is the same for both. This will tell who’s panel is putting out the most. 200w should be capable of around 11.6 amps & a 250w around 14.5 amps (both figures + or minus a bit).