I have talked to two people that have older 18hp models and they have nothing but good things to say about them, however I was told that they have made the 180 a little smaller and the last time I was at Tazwell they had one on the floor and it looked smaller than the 422 to me although they wern't side by side. I went through the same decision process and decided that I would go with the 425 and count the difference as an investment(payments) I am glad I did. I have just finished doing the 50 hour service. servickng it wasn't too difficult everything on the new models is easier to get to ,like the oil filter and the hydrolic filter. In the 50 hours that I have had mine I have moved 27 tons of gravel, dug a septic tank hole dug a 4ft by 8ft by4ft deep overflow hole and covered them up. smoothed the yard back out. I am very pleased with mine. I tried out the 422 at Tazwell and it seemed as though it would have did the same work just as efficiently as the 425, and the same attachments I beleive wouldwork an both of them. The 40 attachments means more versitility. I wish i had tried out the pt180 so I could give you a better evaluation of it. Wish you sucess on what ever ypou decide. Sorry about the bad typing, I forgot to mention that I had did about 8hours of brushhoging.