Your antenna supplier is probably also an U-blox reseller ;)
Seriously - pretty much all cellular modules: Telit, U-blox, Gemalto [former Cinterion], Simcom, Quectel are basically the same (I've tried Telit, U-blox, Simcom and Quectel myself). The basic AT commands (like dial, send SMS etc.) are standarized by 3GPP, and are the same across all modules.
There are very few manufacturers that make cellular chipsets (Qualcomm, Intel, Mediatek - google Apple issues with the supply of their wireless modems). When it comes to single-standard LTE-NB1 modules (not exactly your case) even the chipset inside is identical in U-blox and Quectel.
If the chipset is identical, then without an extra RF-frontend all radio parameters are also identical.
Unless you need a very specific characteristic (like temperature range, special firmware, sensitivity, support, long-term availability and logistics) - I would regard all modules as the same. If a cheaper module works for you - just use it.
You could buy for example 2-3 different development kits and do some testing in the location you plan to install your device to see if there are any measurable differences (assuming same installation, same antenna, same antenna feeder etc.).
Having a GSM/GPRS-only module can be risky, because the old networks are being slowly phased out, so perhaps ask your network operator what are their plans. Norway for example plans to disable 3G in 2020 and GSM in 2025.
The nice thing about Simcom is that some of their modules can be easily soldered by hand, because they only have castellations ("pins") at the edges. It also reduces manufacturing price, because the solder joints are obviously visible, easy to inspect and easy to rework. Forget about that in case of an LGA package from another supplier - you'll need an X-ray machine to inspect the joints hidden below the module.
The nice thing about Telit is that some of their modules are programmable, ie. you can write your own software package that will run on the module itself, so you may not need an external MCU (haven't tried that yet myself).