Mahindra 5155 owner here. As previously mentioned, same chassis as the 5145 you are considering. I can tell you that chances are you would really like the 5145. I believe that anybody who tried out a 5100 series tractor would have to admit that at the very least that they are a very well designed and well thought out machine.
The operators station is ergonomically perfect. Everything is within short easy reach, and at the same time nothing is in the way. The transmission and gear selections are very user-friendly. The 2.7L l-4 has tons of low-end torque, even in it's naturally aspired version found in the 5145. My previous tractor was a Mahindra 4540, which used the same engine as the 5145, with 5 less horsepower. That tractor was not comfortable, or easy to use. But if it was anything, it was tough as nails. I exceeded it's limits and expectations numerous times and it always remained reliable. The 5100 series is most definitely even tougher than the 4500 series, with the features of a premium tractor for a very reasonable price. I live on a mountain and have to drag/haul stuff up it on a regular basis, so I went with the turbocharged 5155 over the 5145. But, my 4540 always did a great job as well.
The transmission was the reason I changed tractors, I needed a shuttle shift for what I do. When I decided to replace the 4540 with a shuttle shift tractor of undecided brand, I closely compared the Mahindra 5155, the JD 5055E, and the Kubota M5660SUH, which are all similarly spec'd machines.
The JD with the 12F/12R PowerReverser trans was $47k.
The Kubota with only an 8F/8R trans was $48k.
The Mahindra with 12F/12R was $36k. Comparably, it has the lowest volume of hydraulic flow at 8.7 GPM, compared to JD's 11.5 GPM and Kubota's 10.6 GPM. But, it has enough flow to operated multiple loader functions smoothly without much decrease in speed. Works for me.
The best thing you can do is to do some research and compare specs between brands. Sit on the different models that you are considering and see what you think of the operators station. I'd definitely try out a 5145 though, they're nice machines.