Hi Dav1,
Politicians in the US at least are notorious for wearing "everyman" watches, Timexes as often as not. Thankfully Timex just came out with a very attractive line of automatic watches if you want to go that route.
I personally would not purchase either of the watches you mentioned thinking about what others might think, but I can certainly appreciate the practical considerations if you simply won't be able to wear it much. In terms of wearability and understatement, the 5157 clearly wins, in all other regards, the 7027 wins IMHO.
The 5157 features the ultrathin automatic movement Cal. 502, so if timekeeping excellence is important to you, it's probably not the best choice. It is much more finnicky and delicate than the manual wind Cal. 507DR so the chances of needing warranty repair or general service earlier are much higher as well. The Cal. 507DR, aside from being beautiful, is an excellent timekeeper as well as being ruggedly overbuilt. It is a new caliber, so perhaps will be even further refined over time, but the amount of R&D Papa Hayek put into it have resulted in a fantastic movement out of the gate from all reports (from watchmakers and owners).
For me, I'd purchase the 7027 without hesitation even if I could only enjoy it in the privacy of my own home and on rare nights out.
_john