Is reach and horsepower that noticeable between the two classes?
Yes it can be and something that needs to be considered. I'll preface that with my current situation in finding a track hoe.
I am about to convert an RPO on a 2011 321DLCR, the compact radius version of a 320. I have rented it for 3 months and decided to go ahead and purchase it for many reasons.
The first and biggest reason is it is not Tier IV and doesn't come with the exhaust after treatment. I looked at 316E's and 320E's but just didn't want the extra hassle and figured this machine (currently at 2000 hours) would get me several years of service before I had to jump into the emissions BS.
I really like the 315 size machine, having owned 2 prior. I would have liked to go with that sized machine but there weren't any available in the shape I would accept through my Cat dealer. The choice to go through the dealer is a business decision that is another topic but I can expound on that if anyone is interested.
I would have preferred that size machine (315) over the 321 for mainly the reason of transport. In the past I have owned a 321, 325 and 2 315's. Now to answer the question about a noticeable difference, yes there is, mainly in the size of the bucket it can carry and the extra production - it will load a truck faster.
Most of my projects are "infill" meaning it is a parcel that had a previous life and with that previous life comes all the buried "treasures". Which means we are undercutting material and bringing in engineered fill to develop the site.
The small increase in production and the fact I couldn't find a decent 315 is the reason why I went with the 321. I hire out the lowboy to move it from job to job or from the job to the pit and this is a cost I can handle since the moves are not that frequent. However, it is more difficult to schedule moves hiring a lowboy as it would be using your trucks to move it. This is something I would think about long and hard. I am not moving frequently, IE every couple of days, the track hoe will be on the site for several weeks or in the pit for a week or two.
On the flip side, I do have a 54K lb tag trailer that moves all of my other equipment. I have a very good friend in the business that does all my dump trucking and he moves my equipment with his truck and my trailer. He uses the trailer to move his smaller equipment as needed and we share in maintenance cost.
The 321 will carry a bigger bucket, has more reach and will be more productive by the stop watch than a 315. That being said, my 315's of the past did everything I asked them to do and were easier to move. The break between those sizes of machines makes it a difficult decision, I hope my rambling helped.
