It has been a while since I've seen the Romulan encounter episodes in TNG... but the impression I have from what I saw was that the Romulans could give the Enterprise a serious fight. There were a few times when a Romulan warship (D'Deridex class) fires upon the Enterprise, weakening her severely. Case in point, in "Tin Man", the Romulans fire on the Enterprise, causing her to take some casualties and disabling 78% of the shields (cited from Memory Alpha). 78% in the first salvo? That's HUGE! Picard realizes it is futile to continue the engagement, else risking total loss of shields, so they back off and let the Romulan push through to their target (the Tin Man bioship). Sure looked to me like the Romulans were coming from a stronger position.
In DS9, the Romulans definitely appear weaker. Maybe they just haven't kept up with Federation technological advances.
In any case, I find the ship designs in TNG and DS9 to be very unappealing. All that open space in the midship section just doesn't look right. The Romulans are the only species that have this design. Then there's also this "artificial quantum singularity drive". It sounds pretty amazing, almost like a perpetual motion machine. I remember something about it never being able to be shut down. Kind of a strange idea, especially when it comes to performing maintenance.
One other thing... always hated the TNG bridge sets of those Romulan warbirds. Looked like something inspired by a clothing boutique.