aftermarket gauges newb

It depends on which gauge. I prefer mechanical because if there is an issue with your electrical system, I don't think electric gauges are going to read properly or they could get damaged if there is a sudden spike in the system. Anything can happen and never say never.

The one gauge I could go either way on is the oil pressure gauge. Using the nylon (plastic) tubing is bad idea waiting to happen. It tends to kink, get brittle and then break. I don't know anyone who is excited about oil on their legs/carpet or floor pan. I been there, done that and washed the t-shirts from the result of it. Never again.
Using one with a stainless line or copper line is a good alternative.

Just buy good gauges and it won't matter which route you go. It doesn't make sense to buy a cheap/inaccurate gauge for something you have your time and hard earned dollars in. Find some good used gauges and go that route. I may be cheap but I do believe in getting the best thing that I can afford lol