Gus, although the Lightsys probably wouldn't be top of my choices neither would the Texecom to be fair. The companies you have invited to quote are obviously comfortable with the product they have specified, you need to be comfortable with the installer.
Many here will have their own opinions with regards the two different systems, fact is both are big brands in this industry and some installers get on better with one brand over another. When I was an engineer I quite liked the Abacus panel and the Castle 2000 series, I hated Menvier panels, and Scantronic 9500 all manufacturers have their own ideas on programming and protocols, and it is entirely down to what you're used to programming as an engineer. All of those panels were very popular at the time.
I really like the Lightsys app it is one of the best apps Ive seen, never seen the Texe app so cannot give a comparison.
Choose the better installer would be my advice, they are the ones that will look after you if they made the wrong panel choice.