Some different ideas are going to appear in this thread. One of the moderators on here has a Husq. and is very happy with it. JD has a tradition of being a quality machine. Let's see if we can get some first hand advice for your inquiry.
I am a JD person and you are comparing two different classes of machines. The John Deere X300 is the first step up from the consumer grade tractors and is in my opinion the best money can buy. The Husqvarna is a consumer grade tractor.
The Husqvarva is very similar to the Sears lawn tractors and has the same size deck as the X300. I just this week replaced my lawn tractor (a John Deere L-120) with a X320. I need a larger lawn tractor as I mow my yard and with 2 and half acres I want to get done as quick as I can so I have time for my family and there times of the year when the ground is wet that I can not use my still larger John Deere 2305 with the 62 inch deck.
The difference comes down to the quality of the machines and the dealer. I find that the John Deere is many times more responsive to me then a box store can ever be and the Husqvarna is a box store tractor.
The other difference is the fact that the John Deere uses the Kawasaki engine and after only a couple minutes on it you will really like the smoothness of this tractors engine compared to the Briggs that the Husqvarna has on it. The decks are also completely different and of different quality.
One other thing is the fact that JD is offering 4 year 4.9% interest on buying a new X series tractor so for approximately 72.00 a month you can have a Deere or if you want to go Whole hog like I did for around $90.00 a month you can get a X320 ($4,100.00) which brings into the game a larger deck 48" into the game.