I've had the Crossman 2300S for a few weeks. I really like it. I ordered the GravMag from the chap in Great Britain. It came in this week. The mag is very pellet specific and most of my pellet varieties won't work in it (.177). I do have some flat heads that will feed in the mag. Frankly, if one were to simply look at the two pistols you'd think the Diana was the more expensive.
You can see I've added a Match Dot II to the Crosman. The Crosman was nearly 2.5x's the price of the Diana. The Diana fit and finish (metal) is better. While the Diana stock is beech, it is finished quite nicely and feels good, albeit just a bit beefy for my medium-sized hands. The Diana is on top.
The only bad thing for me in these recent purchases, I ordered a Diana Airbug from airgunns.com (yep, 2 s's) on December 22nd. I still haven't received it and the vendor isn't returning e-mails, there is no phone number, and lo and behold, when I googled reviews for this vendor, they aren't good. So, I ordered the 2nd one from PyramidAir with whom I've bought many airguns in the past.
I'm going to shoot these through FX chrony at 10 paces with a rest for accuracy and "power" comparison. I'll report back here with what I find.
BTW. I can't believe the Diana is so economical at $129! I bought my grandson a Chaser for Christmas. I'll probably put it through the same comparison as I note above.