Hi. Maybe this is will be off the mark, but am I right in guessing that there is latency to all of the keys and buttons on your controller? And, is the latency only in the audio, or is it in any DAW visual displays as well? I'm guessing it is only the sound, and that's because it's really the sound driver that is slow, not the MIDI.
There might be some exceptions that I don't know of, but one controller shouldn't really have more latency than another. The good news is, the latency is fixable with a driver download, if it's the common thing. Sorry for assuming, but I'm guessing you're on Windows. The following may be similar for a Mac, but I'm not sure.
That is, the driver being used by your sound card or interface, if you haven't addressed this, is probably one that is not designed for low latency sound production, and there is a generic driver that adequately solves this for people just getting started. The thing most people do is install the ASIO4ALL driver. That is what I did when I was using FL Studio and found that my controller had latency.
It is the same in REAPER. In your options, in Devices, there is a setting for sound device driver. Once you download and install ASIO4ALL, you can choose it as the driver (*check to see if it's already there, first). It was created to let the common person's sound card work somewhat like a fast audio interface. You will have ASIO options accessible in REAPER's device options and as an icon in your taskbar when it is being used.
In those options, you want to click and light up the sound device or devices that you are using and the appropriate inputs/outputs. A lot of the time, for me, the DAW will only work properly when only one device is enabled, but it depends on what I am trying to mix and match. I am able to use my PC's integrated soundcard as the main device while using the inputs from my audio interface, and that works, but if I try to also enable inputs from another USB stick, I get no sound from REAPER.
Once you get your devices/inputs selected (no MIDI involved, BTW), then you want to set the buffer size for the devices in the ASIO4ALL panel. This is the setting that determines the latency. At stock settings, it will probably be a lot faster than the standard Windows driver, but lowering the buffer size can make it even faster, but you don't want it to be so fast that your computer can't keep up with it, or it'll crackle. On a fast computer, 88 is a good area to be in, but maybe that's just on mine.
Just so you are aware, a problem that is created by using the ASIO4ALL driver is that when the DAW is open and using the driver with your sound device, all other computer sound except the DAW will not play through the device. It's either ASIO or everything else.
To deal with that, I use a mini USB sound output (
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1) and a joiner cable (
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1) and I make my PC's sound to go out the USB stick and join the signals together before going to my speakers. It works like a charm, so I can still check out Youtube while in REAPER.