Stick with the M350. Here's my reasons, first and foremost, cost. Beeman Kodiak/Webley Patriots (by virtue of their discontinued status) demand a high (and rising) price on the classifieds, when you're lucky enough to find one. Even if you sell your M350, you'll still have to lay out some serious cash to get one. .22 cal pellets are cheaper, so if you do a lot of plinking, cost will add up. There are some very accurate high quality pellets with good BC, that should maximize your plinking range in .22 .25 will drop faster. If you can't find a Patriot/ Kodiak, there are only a few other really hi power .25 spring/gas rifles. The Turkish WFH ( reasonably priced and gas ram upgrade available) has at best, mixed reviews. The Benji Trail XL has virtually no reviews in .25 and .22 are mixed as well. You can plunk down 4 figures for a .25 Theoben Eliminator/ Beeman Crow Mag (new, used aren't quite as much). The Gamo Hunter Extreme is available in .25 too, but I don't know if it's worth the $500 asking price.
Just my opinions, others may differ