I just returned to brewing after being away from it for 5 years. I just brewed this past weekend and have 1 lager and 1 ale fermenting now (middle of the road beers - nothing heavy or light). Here's my comparision:
Before, from detailed notes I kept, this was my general procedure: I used the smaller Wyeast starter packs (that's all they had back then) or White Labs tubes and always made a starter. I did middle of the road lagers and ales (no high gravity stuff). I just agitated the carboy to get it aerated (no airstones or anything like that). I would have yeast activity (airlock liquid movement, yeast dust on sides of fermentor, etc) within 6-8 hours and very noticeable to full blown activity within 10-12 hours. Ale fermentations would wane after 3-4 days, lagers after 4-5 days. If I let the finished beer sit on the yeast cake 2-3 weeks after fermentation ended (hydrometer confirmed) before kegging, the beer tasted better; if I kegged it right after fermentation ended and waited same amount of time, the beer tended to not be as good.
This past week, I used the larger Wyeast Activator pack for the first time. Did not make a starter as advertised. I did not read the date when I bought them (too excited to care) but they sat in my fridge door for 2 weeks (the one my kid opens all the time and sometimes shuts...when she remembers). I popped them both when I began heating my mash water. By pitching time 5 hours later, they were all blowed up and so I dumped them in (60 degree wort) and agitated the carboys just like I done before. This was about 6:00 pm. At 1:00 am, the liquid in the airlocks on both had moved slightly (due to pressure) and a light dusting of yeast was visible on the sides of the fermentor. Next morning (8:00 am), low level fermentation was ocurring in both (airlock bubbling slowly, wort cloudy w/yeast moving slowly around, thin cap forming). By afternoon, full blown fermentation, cap, farting yeast smells, etc on both. Ambient air in the garage was 60-65 degrees. As of today, the ale looks about done and starting to clear with only an occaisional bubble; lager visibly winding down and looking like the diacytal rest will be coming soon. Both will sit on the yeast cake 2-3 weeks before I rack.
By my math the difference in lag time was just a few hours. Will that transfer to the finish flavor? Possibly. But my past experience tells me that 2-3 weeks on the yeast cake has a far more noticeable impact on flavor, curing or minimizing many a flavor problem. So, that's where I will concentrate my efforts and not worry too about the starter and a few hours difference in the lag time.